Article by: Perry Romanowski

Here’s the biggest difference between what you experienced in your college organic chemistry lab versus a cosmetic formulation lab. In an organic lab, you mix chemicals together and hope something happens. Ideally, you get a chemical reaction you expect. As a formulating chemist, you mix chemicals together and hope nothing happens. Cosmetics are mixtures of chemicals that mostly aren’t supposed to react with each other.

Unfortunately, they often do react (or otherwise change) so you need to test your formulas to see how long they will last. This is called Stability Testing and is something a cosmetic scientist spend much of her time doing. In this post, we’ll give a brief description of the test and suggest when, why and how it should be done.

What is stability testing?

Stability testing is simply an experiment in which you create a batch of your formula and put samples of it at different environmental conditions for a set period of time. These conditions vary in temperature and light levels and are meant to simulate what will happen to the product during its life cycle.

At select intervals you evaluate your samples for various physical, chemical and performance characteristics to see how they have changed. If the changes are minimal according to your company standards, then your formula is said to have “passed” stability testing. This means you can have confident that when the formula is shipped to stores and ultimately customers, it will still be as good as when it was first manufactured.

The underlying assumption in stability testing is that increasing storage temperature speeds up any aging reactions that will occur. A handy rule of thumb is that a sample stored at 45C for 8 weeks is equivalent to one that is stored at room temperature for one year. This isn’t an exact predictor, but is good enough for the purposes of cosmetic products.

A sample stored at 45C for 8 weeks is equivalent to one stored at room temperature for a year

When do you perform stability testing?

Since you’ll be making hundreds or thousands of prototypes during your career, it won’t be practical to run a stability test on all of them. You’ll also find that changes happen so rapidly at your company, you won’t have time to properly test many of your formulas. But there are times when you need to do stability testing. Here is a short list of some of the most important times to conduct a stability test.

1. New prototypes — Whenever you make a new formula and are satisfied with the way it performs, you’ll want to do a stability test to ensure that it will stay together. Don’t bother testing all your prototypes, just the ones that work the way you want.

2. New raw materials — Whenever you have to change the fragrance, color, or other raw material in a formula, you’ll have to do a stability test to make sure there aren’t unacceptable changes. Also, when you have a new raw material source (or supplier) you’ll want to run a test.

3. New manufacturing procedure — Manufacturing is always trying to find faster ways to make formulas. This often means they change some order of addition or shorten mixing time. Whenever changes like these happen, it could affect your formula. Run a stability test to see if the change is acceptable.

4. New packaging — Cosmetic products change their look almost yearly so packaging is constantly being modified. Whenever you get a new package, you’ll have to determine if the formula continues to be compatible. Stability testing helps ensure that it is.

How do you stability test a cosmetic?

There are no set rules on how you must conduct a stability test for cosmetic products. Of course, for cosmetic OTC products like sunscreens, AP/DO, or dandruff shampoos the FDA has specific stability test requirements that you have to follow. See the FDA website for more information.

Here is a basic format you can follow for conducting a cosmetic formula stability test.

Step 1 — Make your batch. Calculate how much to make based on the number of samples you’ll be using for the test. It’s a good idea to make 30-40% more than you think you’ll need.

Step 2 — Fill your samples. Ideally, you’ll have the correct packaging but don’t count on it. When appropriate, fill glass jars with the product along with the finished package. In stability testing, you want to do both glass and packaging if possible. The number of samples depends on how much testing your doing but at minimum you should have 2 samples for each storage condition.

Step 3 — Take initial readings. Once you have a sample filled test it for all the characteristics you’re going to evaluate later. The exact tests depend on the product but minimally you’ll want to record notes about the appearance, color and fragrance. You’ll also want to take pH and viscosity readings. For aerosol products you will test spray patterns.

Step 4 — Put samples at different conditions. Stability testing requires different temperature and light conditions. Some standard temperatures include 50C, 45C, 37C, 25C (RT), and 4C. You’ll also want to conduct a freeze/thaw stability test which involves cycling your product through 24 hours of freezing then 24 hours of thawing. Different lighting conditions involve a fluorescent light box and a natural light box (to simulate sunlight).

Step 5 — Evaluate the product. Samples should be evaluated at the following intervals. 2 weeks, 4 weeks, 8 weeks, 12 weeks, and 52 weeks. Only the RT, 37C and 4C samples will be evaluated after one year. The highest temperature samples and the light exposed samples only need to be evaluated for the first three test intervals. The evaluation tests should be the same ones you conducted when taking your initial readings.

Step 6 — Determine stability. After 8 weeks you can confidently decide whether your formula is stable or not. Nearly all products will exhibit some change so it will be up to you (and your boss) to decide whether the product passed or not.

Early in your career, stability testing will be one of the most common activities you’ll do. If you can create a system that you consistently follow, you’ll avoid burn-out and be able to confidently communicate when a product is appropriate to launch.

How does this compare to your company’s stability procedure? Leave a comment and let the rest of the cosmetic chemists here know.


  1. Jagdish Jaiswal

    Is Freeze Thaw applicable for Bar Soap?

    1. Perry Romanowski


  2. Neha

    I am preparing body wash using biosurfacant and CAPB ,oil and i am facing problem of seperation pplease do let know how to stabilize the emulsion

    1. Perry Romanowski

      You’ll need to provide more information than that. The answer depends on what oils you’re using and what emulsifiers you have. I’d suggest you post your question in our forum.

  3. Marija

    What would be a good stability test for evaluating wet wipes shell life?

    1. Perry Romanowski

      You’d have to base it on the procedure outlined in this post.

  4. Shekin

    Hi Perry, is humidity an important of stability study? Or I can just use an oven instead of an incubator to conduct stability study? Thanks!

    1. Perry Romanowski

      For most products, humidity is not that important. But for stick products or other things that are affected by moisture absorption, then it should be considered.

  5. Ajit

    Mentioned “A sample stored at 45C for 8 weeks is equivalent to one stored at room temperature for a year. ”
    Request if available any supportive documents Please attached link .

    1. bryan

      i thought 45C 3 months is equivalent to 1 years at 25C instead based on Arrhenius law where every 10C double the reaction.

      1. Perry Romanowski

        The rule is based more on experience than math but you’re free to follow the 3 months at 45C = 1 year at 25C.

        In manufacturing, companies are keen to get answers more quickly.

  6. Julie

    Hi Perry!
    Is it acceptable for a small handmade company to conduct their own stability testing in their studio/lab for physical changes, or is a certified document required from an outside lab to provide results? Thanks for any insight!

    1. Perry Romanowski

      Yes, as long as you follow a specific protocol that you’ve written out and you keep good records. The test you follow should also be a reasonably good stability test as the one outlined in the post above.

  7. Fernanda

    I’m developing a lipstick and when I put it in 40°C it become completely liquifier. What should I do? Can I say that my lipstick it’s not conforme? How can I evaluate my sample in 40°C ? Do I need evaluate as soon as I pull it out ?

    1. Perry Romanowski

      This is an interesting question. You have a few options.

      1. Change the formula so it does not melt at 40C. That is much too low of a melting point for most products.
      2. You can pour the melted lipstick sample into a mold and cool it down before evaluating.
      3. No, evaluations should be done at room temperature

      But I think you need to change your formula. Lipsticks should not melt at 40C. It is reasonable that some consumers will find their products get that hot in the real world and this could lead to a significant mess.

  8. Babak

    what kind of a stability test is the best should do for an anhydrous cream system with silicone and oils inside?

    1. Perry Romanowski

      The stability test outlined here would be good

  9. Joanna

    I’ll plan make a fresh cosmetics it means: Date of Minimum Durability is 6 months. Now I have a question about challenge test – should I do it for my cosmetics when date of expiration is short. Next question about safe raport for cosmetics. I’ll plan make indywidual cosmetic for clients it mean thah each cosmetics are different and I haven’t idea what should I do with raport – do for eevery products?it will impossible. Could you help me please.

    1. Perry Romanowski

      Yes, you still have to do stability testing. You have to be able to prove your products are safe.

      I don’t really understand the rest of your questions.

  10. Rebecca

    Hi I wonder if I can post on here or if I am too late.. I have many formulas that have been tested and lasted one year but all of them are under normal conditions e.g 20c-25c room temperature. Do I need to also test them at accelerated temperatures or is this sufficient for a 1 year expiry? Any help would be greatly appreciated, I can’t find anything in the UK..

    1. Perry Romanowski

      If you specifically set up a test where you can demonstrate that your products are still stable after a year then that would be adequate for the US. I’m not sure for the UK but I think that would work. You’ll need to get it approved by the inspectors.

  11. Tanya Ross

    Hi Perry – could you possibly update this post to include a link on where to purchase the required equipment to store samples at elevated temperatures? I assume this is some type of incubator perhaps?

  12. Abdul rouf

    hai perry ,
    I need tests for cosmetics like hand & body lotion , scrubs, hot oil cream etc. what test can we do?
    how centrifuge testing is done? please specify the source for centrifuge.

  13. TSAKI


    1. Perry Romanowski

      Follow the stability test protocol above. Also, be sure to document what you are doing. Additionally, you need to do microbial testing and a preservative efficacy test. Finally, if you are making any claims you need to demonstrate that what you are saying is true.

  14. Kimberly

    Hi Perry, our product has finished the first 4 weeks of stability and has held up stably in heat, however the colors have shown fading. Is this normal?? We’ve have already placed our payment for production and we are in such a tight timeline. How can we approach this problem?? Please help!

    1. Perry Romanowski

      That’s normal for a product that fails stability testing. If you have the product in opaque packaging, it may not be as significant a problem as consumers may not notice. But that might not work. Without knowing what’s in your formula I can’t offer much other help. I’d suggest you post your question in our forum.

  15. Abiola Adebayo

    If you’re not adding chemicals and just doing homemade items like liners and lip balm , lip scrubs with all natural organic materials , do you need to do any chemical testing?

    1. Perry Romanowski

      Yes. Everything is a chemical. It is illegal to sell unsafe cosmetic products no matter where you make them or what you use to make them. Everything has to be proven safe.

  16. NaNesha Perry

    Hello Perry, I want to start liquid lipstick line what test should be done and what products are needed?

    1. Perry Romanowski

      I’d suggest you post your questions in our forum. Testing needed would be stability testing, safety testing, performance and claims testing.

  17. Jo

    Hi, if you change the same non organic ingredient to an organic one, does it require another stability test (and a new assessment?) thanks.

    1. Perry Romanowski

      Yes. A stability test is required whenever you make a change. Even if the change is just a new supplier of the same ingredient.


    Hi Perry,
    Quick question, when we do stability for personal care products at 40C temperatures for 12 weeks does it correlate to 3 years of shelf life? I am being told by one of my vendors and not have heard that before.

    1. Perry Romanowski

      I wouldn’t rely on 40C for 12 weeks equalling 3 years of shelf life.

    2. Rameshchandra

      If you do stability for 28days at 45*c ,the product self life for 3 years in oralcare

  19. The Opulence Skin

    Hi Perry,

    Thanks for sharing on how to do a stability test a cosmetic formula. This will come in handy for our skin whitening products here in the Philippines.



  20. Rebecca

    Hi There

    I’m so glad I found you!

    I have some questions regarding stability testing..

    What PH range should say for example a cream or lotion be for the skin?
    If a cream isn’t stable for 1 year, but is stable for say 6 months, does this mean it could be sold/used and the expiry date could be 6 months, or does it mean it is not fit for sale/use at all?
    If a cream is a creamy colour and lightens after 6 months, again does this mean it can be sold/used with a shorter expiry date or not at all?
    Again the same question for the scent.. if it is fine after say 6 months but deteriorates after 1 year, can’t I just have a 6 months expiry date?
    I am in the UK (I’m assuming you are in the USA?) and here I have not been asked for temperature test results so I am just testing at room temperature for 12 months plus buying PET (preservative efficiency tests and CPSR’s (cosmetic safety reports).

    I want to make sure my blends will ‘pass’ with my stability results before I order PET and CPSR’s..

    Many thanks in advance!

    1. Perry Romanowski

      The pH range depends on the composition of your cream. But pH 4 – 6 is reasonable.
      It’s a matter of what risk you are comfortable with. I wouldn’t sell something that wasn’t stable for 1 year.
      A color change is a matter of aesthetics. If your customers don’t mind the change then it’s not a problem.
      Same with scent
      Whether they pass or not will depend on the regulator you hire and what they believe is correct.

      Hope that helps

  21. Nikki

    Hi Perry, Is there and facilities in the metropolitan area of New York that you would suggest for stability testing? I’ve called up labs and they’ve all said no the don’t do it in New York City.

    All the best!

    1. Perry Romanowski

      Sorry, I don’t know of any place. But maybe someone will see this and contact you.

  22. Maria Miller

    Hi Perry, I am a little confused. On certain posts you say 45c for 8 weeks and for others you say 45c for 3 months (12wks). I am trying to create my accelerated testing schedule for 50c. (unable to do 45c, there is no setting for my heat/cold fridge) I need to know which calculation of yours to use as a base for my 10x reaction rate. Thanks for your help

    1. Perry Romanowski

      There is no official calculation. The 45C for 8 weeks is just a guideline and will not be true for every formula. 50C is probably too high to test for stability but 50C for 8 weeks would be a good approximation for 1 year at Room Temperature. But it’s just a guess.

  23. Catherine Banks

    Are accelerated stability tests reliable? I have a facility willing to do a 3 month test in only 21 days – are the results going to be accurate? Time is of the essence, but I also want to make sure the product will hold its quality.

    1. Perry Romanowski

      The results may or may not be accurate. I wouldn’t trust the results but some people might.

  24. DINA

    hi Perry, if i have done stability testing in real time study (30 C 1 year) and the result is good, so how do i determine the shelf-life of my product? Thank You

    1. Perry Romanowski

      Well, you can say it’s stable for at least a year if you’ve done that testing.

  25. Venkat

    Hi Perry, Drug stability testing requires that production line batches be used ( 3 batches, according to FDA 25000 to 50000 pellets or capsules / batch) and assessed for stability. Do cosmetic products also need to be stability tested with 3 batches from production line or can we prepare few samples ( 40 to 50 facial cream) in non-production line ( production line simulating system) system then use them for stability testing. Thanks

    1. Perry Romanowski

      There are no specific stability requirements for cosmetic products. The PCPC has some recommendations but the format suggested here is what some companies use.

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  27. MrScientist26

    Hi Perry, Just would like to ask if stability evaluation is required on the finished goods if you used material which was retested several times? How about usage of expired raw material that passed retesting? Thank you very much.

    1. Perry Romanowski

      It’s a matter of risk. It’s good to run a stability test on your production batch, but if you’ve already passed a stability test with the formula you can ship before the results of your production run stability batch. As far as expired raw materials, if they pass a retest then an industry standard is that they are probably good for another 6 months. But this depends on the ingredient of course.

  28. Samantha

    Hi Perry, I would like to ask body lotion that viscosity drop and separation when in the incubator 45C in 1 week but when its back to RT become normal standard viscosity. Its that consider stability failure? Thank you.

    1. Perry Romanowski

      No, this would not typically be considered a stability failure.

  29. aya

    hallo Mr.Perry Romanowski thank you for the information, but I have a question please, I am college student who is making an internship in a small cosmetic company and I really want to make graduation project in this company but I am kinda lost what to do exactly for a graduation project, please due to your experience if you have any idea for a graduation project that is related to cosmetic industry please yyour help will be highly appreciated
    thank youuuu

    1. Perry Romanowski

      Hello – there are lots of things you can do. Maybe you can learn to formulate a body wash or skin lotion. Or you can test the foam quality of different shampoos.

      1. Marie

        Hello Perry. I need small quantities of preservatives to do my trials, can you recommend a provider that would do small supplies? Thx!

  30. Khaled

    if stability is done at 50°C for 8 weeks, would it be considered stable for 3 years? and if yes, should we set a specific humidity percentage ? knowing that currently we perform testing at 45°C for 12 weeks to predict stability for 3 years duration and humidity percentage is not set.
    Thank you

    1. Perry Romanowski

      No, 50C for 8 weeks does not equal 3 years of stability.

      1. khaled

        kindly is there any suggestion for an accelerated stability method for a period of time shorter than 3 months ?

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  32. Dakalo

    Hi Perry, thanks for all the info provided so far.

    My question is regarding stability tests results. If my product has a pH spec of 5.5 – 7.5 and in week four I get pH lower or higher than spec on any temperature, does that mean my product is unstable? My understanding is that pH and Viscosity will move either up or down depending on product and the issue might be that during production the parameters where more towards the min or max side instead of being on or closer to the target. Is my thinking correct?

    1. Perry Romanowski

      When you are doing stability testing you should set a specification range and if your formula goes outside that range, it’s consider unstable. But if the performance of the formula isn’t significantly different then you can just reset your range to include the changes. It really depends on the product and the risk taking tolerance that your company has.

  33. Lindsay Lipp

    When stability testing, is it customary to allow the heated samples to cool to room temperature each time before taking viscosity/pH?

    1. Perry Romanowski

      Yes, all samples should be tested at room temperature.

  34. ahmad bakhsh

    I have collected many creams from market some of them change color when exposed to sunlight. the upper most layer of cream either turns grey to black of light yellow to brown.
    1. Is the benzophenone -3 can remove this problem?
    2, which ingredient is the reason of this color change?

    1. Perry Romanowski

      You haven’t provided enough information to answer your questions. Benzophenone might help or maybe not. A likely reason for a color change is either a material in the fragrance or something in a natural extract.

    2. syed arshad

      you must add tris tetramethylhydroxypiperidinol citrate

  35. Sabreen Ahmad

    Dear sir,
    I have a problem with facial milk(cleanser like cream) actually it separated after few months of successful emulsion , it has carpapol in purified water, I think that the problem may be due to excess water use what do you think?
    Hopefully to hear from you!

  36. SM

    Dear Perry
    Ifound ur information really useful.Thanks a lot.I have a question.Can u help me with aerosol spray stability?Should we put the whole can in the oven?For how long?Isn’t it dangerous?
    We produced anti perspirant spray & after two weeks whols were appeared in the cans.Can u help me with this problem pls?INGREDIENTS(PROPANE,BUTANE,ETHANOL,IPM,PG,ACH,PERFUME)
    Thanks again.

    1. Perry Romanowski

      Yes, you put the whole can in the oven. It shouldn’t be dangerous. If you have any problems then you are clearly using the wrong cans.
      If you are getting holes in your cans then there is something in your formula that is causing corrosion. This is a failed stability test and you’ll need to reformulate (or get a lining on your can).

  37. usha prasad

    Hello , Is there any stability test for Kum kum powder and and about shelf life

    1. Perry Romanowski

      Just follow the test outlined above.

  38. Ahmad Bakhsh

    Dear Sir,
    Please send me the testing stability methods of creams,lotions and face wash.

  39. Mike

    I also have a question regarding this usefull rule of thumb about sample stored at 45C for 8 weeks is equivalent to one stored at room temperature for a year. Are there any litarature references that support it?

  40. Mike

    How much airspace would you leave in a stability vial to be placed in the oven for the 45C testing? The headspace of the vial may affect the stability. I think that if a future packaging is tube, then minimum airspace should be left. Consequently there should be one vial per test. Also content uniformity also should be tested by opening a new vial and taking top-middle-bottom samples every time. Does this make sense?

    1. Perry Romanowski

      Yes, this makes sense. However, it is probably more testing than you really need to do as there aren’t many changes that you’ll see that standard single sampling will miss.

  41. Maria

    Since I discovered your site I am an incondicional fan of it! Thanks a lot!
    I would like to know if your recommendation for stability test (especially freeze/thaw stability test, 45ºC test) can be applied to solid formulas like soaps in a similar way.

    Thanks again!

    1. Perry Romanowski

      Yes. You just need to have some type of measurement so you can determine whether the formula passed or not.

  42. Eva UK

    Hi Perry,
    I am testing under UV stability some lotions, checking the discolorations that the fragrances 0.1% would bring to the product.We have accelerated UV conditions of 40W/ 365nm .Here I need your opinion!
    What do you think of 72 hours of UV testing, for what period of normal UV exposure is this equivalent?
    Would you recommend other wattage for the UV light while testing lotions?

    Thanks in advance
    Eva UK

    1. Perry Romanowski

      Hello Eva – I don’t really have an answer. We tested our UV samples for 8 weeks and figured that would match 1 year of actual exposure. I don’t recall what the lighting wattage or wavelengths were. I would suggest you post this in our forum.

  43. Azmar Ahmad

    Hi Perry!

    “Step 5 — Evaluate the product. Samples should be evaluated at the following intervals. 2 weeks, 4 weeks, 8 weeks, 12 weeks, and 52 weeks. Only the RT, 37C and 4C samples will be evaluated after one year. The highest temperature samples and the light exposed samples only need to be evaluated for the first three test intervals. The evaluation tests should be the same ones you conducted when taking your initial readings.”

    I am currently formulating emulsion using natural ingredients. Most of the stability tests guidelines I found are for pharmaceuticals products which takes minimum duration at least 6 months. Your guideline given is pretty much alike to be used for my product. According to your Step 5, you use 2 week intervals. I would like to know what is your reference of the duration?

    I’m looking forward for your prompt reply.


    1. Perry Romanowski

      This is just what we did at our company. 2 weeks is not long enough to make a decision about whether the product passes stability but it does give a good indication if it will fail.

      1. Azmar Ahmad

        Thank you for replying. 🙂

  44. joanne nguyen

    Hi Perry ! if my cosmetics products is fail for a lab test, do they give me a chance to redo ? Thank you very much !

    1. Perry Romanowski

      That depends on the testing house but probably not.

  45. oreather taylor

    Thank you Perry:
    you have been very helpful to me. From reading your blog, you have answered all my
    questions about stability testing.

  46. ushaprasad

    Thanks for the information.

  47. Taluker Mizan

    What red color i can use for Ph 12?Please help.

    Talukder Mizan.

    1. Perry Romanowski

      What product is pH 12?

      1. Aly kay

        Is there a place where I can take homemade creams (that I purchase ) to get dissected and to find what ingredients are in the cream?

  48. Kapil

    Dear Perry,

    I have a question.

    Suppose we have 2 same category cosmetic products (for e:g; facewash), one of them has stability of stability of 2 years and other has 4 years.

    What can be the possible reasons for this difference in stability time.?

    1. Perry Romanowski

      Well, that depends on how you measure stability. It really depends on the specific chemicals that you are talking about.


    hi sir.. may i know how did you compute for the equivalent years the product will be stable from a certain temperature and days??? thank you

    1. Perry Romanowski

      There is no mathematical formula that works for every formulation. A rough guide is 45C for 8 weeks = RT for 1 year but this is just a rough estimate.

      1. Hiren

        Then why it is different for RX product and OTC product in that case if you put at 45 c for 3 month it will good for 2 year why they have descripnacy in those

        1. Perry Romanowski

          There is a discrepancy because there are no official rules for cosmetics. They are only rules of thumb.

  50. Abhijeet Gupta

    Hi Perry…i came across a term “full turnkey formulation equivalency / alternate raw material testing services”. Can you throw some light on these.

    1. Perry Romanowski

      that just means the contract manufacturer will give you a stock formula to match your concept. If your focus is on marketing this is a good option for you

  51. nasrin

    you mean that with havine some changes in our emulsions however it passes the test?

  52. Kumar

    I want to know that, why creams will separate after few months after successful emulsion also?

    1. Perry Romanowski

      It really depends on what’s in the formula but basically it is because emulsions are inherently unstable.

  53. Jorge Castro


    Is there any correlation between UV chamber testing times and shelf-life equivalent for UV light exposure?

    1. Perry Romanowski

      There is no correlation of which I’m familiar.

  54. Adrianne

    A customer would like a 3 year expiry date for there cosmetic product. How long do you recommend doing an accelerated stability test (45C) to obtain a relatively good prediction?

    1. Perry Romanowski

      Maybe 16 or 20 weeks? I don’t really know though as lots can change at 45C when stored that long.

  55. Lieve

    Dear Perry,

    I have put W / Si Foundations for 3 months at 5 ° C . ( Also at 20°C and 40°C but the customer prefers to keep the samples at 5°C ) Do you have an idea what would be the predicted shelflife for these foundations?

    Thanks a lot in advance !

    1. Perry Romanowski

      If the shelf life is from the perspective of someone who bought the product the 40C results are much more important. 5C is not predictive of future stability. Only accelerated temperatures are predictive.

      If your customer is storing the product at 5C and it’s stable for 3 months, it’ll probably be stable for at least a year. I don’t know for sure however.

  56. R.Swaminathan

    Dear Sir
    Good information and useful to all Cosmetic professionals. I have one issue- the Oil in water emulsion product- Hair cream , Beauty cream etc.. if we are keeping the sample ( well sealed product) at 45 deg.c for 6 months- to know the stability after 2.5 years- the stored products – turned to thick due to water evaporation. How can I perform the stability study for said cream… Also, is there any norms for storing the FG – cream/ face powder for filling. As per Microbiology norms- to get the complete status about Pathogens / Fungai- we need to wait min. 5 to 7 days. Is it okay to wait and fill or we need to fill immediately or any norms for it. ( we need to fill with 48 hours or 24 Hours like ) Best wishes.

    1. Perry Romanowski

      You don’t have to wait to fill but you are taking a gamble that the product is going to be safe. A contamination check should not take 5 to 7 days though.

      If your product lost that much water to evaporation it’s likely that your packaging will not be adequate for good stability over 2.5 years.

      1. R.Swaminathan

        Thanks for your quick response.

  57. Toor

    Mr. Perry, nice informations from this site. We have 2.5 years expiry date of our perfume sprays so please explain how much time will be the best for 2.5 years expiry. Thanks in advance

    1. Perry Romanowski

      Well, you likely have to do at least 6 months of stability at 45C

      1. Toor

        Thanks for replying, I want to make my stability procedure for testing Perfume Spray, Perfume Oils, Perfume Solid Cream and Perfume Gels. I need standard guidelines like FDA as reference for that procedure. you suggest for 6 months stability testing period for 2.5 years expiry, can we test for 3 months or less and which types anomalies can occur.

        please advice and thanks

  58. Marina

    I love this article, but wasn’t able to find information on what type of ovens to buy to do the stability testing at home? I know using my cooking oven is not good. Do you have any suggestions? thanks

  59. shirley

    hello perry,
    when running heat stability test for stick products, like lipsticks, eyeshadow pens, etc,. how should we place the sticks or pens in oven? horizontal? or vertical? or other different ways?

    look forward to your reply.

    thanks, shirley

    1. Perry Romanowski

      Hello shirley – Ideally you would do it both ways but if you had to choose, I would go with having them standing up the way they’ll be displayed on the shelf.

  60. shirley

    how to determine the length of PAO for each category, for example, 6 month of PAO for mascara and eye liner, why 6mo? but not more or less? 24 month of PAO for face powder and blush, why 24 month?

    1. Perry Romanowski

      Good question. Each company chooses their own level of comfort for making a claim they can support. If you want to test for 24 months & can prove it, then you could use that. Most companies don’t want customers to go 2 years between purchases so they put 6 months on there. There are not really any specific rules.

      1. Rajeev Bhardwaj

        What will be the exact wordings sahll be printed on the primary or secondary packing material of any medicated cosmetic products ( manufactured under cosmetic lic.)for those be given to the doctors like
        Free sample not to sold or Free sample not for sale

        1. Perry Romanowski

          I don’t know. It depends on what you are selling.

  61. Chelsea

    Hi Perry,

    Would appreciate if you can share with me how to do the stability testing for wet wipes (water-based). Is there any specific guidance?

    Hope to hear from you soon.
    Thank you.

    1. Perry Romanowski

      Hello Chelsea,

      I haven’t specifically tested wet wipes but I would model it after the procedure listed above. Be sure to do microbial testing initially and after 8 weeks. Store samples at different temperatures and run specification tests after each checkpoint.

  62. Vida

    Hi Perry !
    Thank you for this chemist’s corner. It is very helpful. Great work.

    Now my question: How long after making a perfume do you conduct stability test?
    Do you have to wait until it has matured or can the stability test be done straight away?


    1. Perry Romanowski

      The stability testing can be done after 24 hours of making the perfume.

      1. vida

        Hi Perry,

        Thanks for your reply.

        When distilled water is used in making perfume, is the preservative testing a must under EU regulation or just stabiity test is needed?

        1. Perry Romanowski

          Preservative testing is part of stability testing.

      2. Teresita Miranda

        Hi Perry,
        Do you know of a protocol in measuring pH and viscosity of lip balm – waxy/solid (if these parameters are at all part of the stability testing process for this product; client desires no shift in pH and viscosity). I was thinking about texture analysis in lieu of viscosity?
        Thank you,

        1. Perry Romanowski

          Typically, a penetration test is done not a viscosity. pH is not really relevant if the product is anhydrous.

          1. Unique

            Plase Boss, What cause a body cream and lotion to change colour from (white to golden brown) when hydroqueno is added and what can be used to sabilize the colour effect.

          2. Perry Romanowski

            Sounds like a oxidation reaction. You need to add an anti-oxidant (BHA or vitamin E perhaps)

  63. Kasia

    Perry do you speak polish. I really need to understand well all the testing process ASAP.

    1. Perry Romanowski

      Hello Kasia – sorry I do not speak polish.

  64. ChemWizard

    Hello Perry,
    What would be the minimum samples required and what kind of Parameters should be tested, while doing a Packaging Testing for Cosmetic products.
    Can you guide through some link or websites as well?

    Thanks so much!

    1. Perry Romanowski

      The samples can be found in the post above. For packaging we used 12 samples for weight loss studies, then about 35 more samples for the stability test. I’m not familiar with a website that lists packaging stability testing.

      1. ChemWizard

        Thanks Perry…

        May I ask why 12 samples?? Would that be for different Orientation?
        Also, what are the Temperature conditions for Package Stability?
        Would you do a Freeze Thaw for the same , just like Physical stability?

        Kindly advise.

        Thanks so much

        1. Perry Romanowski

          We put 4 samples at three different temperatures. 45C, RT, and 4C. That is just to give us confidence that all the packaging would behave the same. You could probably do less.

          Package stability uses the same temperatures as listed in the post above.

          Yes, we did Freeze Thaw studies for packaging too.

  65. swatika

    hello perry
    we are a fragrance manufacturing company in India, however, in application department we are taking trials of almost all the products including personal , home care categories.
    After going through your various discussions on stab data protocol, would like to know about the fragrance retention part in stability process, I mean the same protocol, shall we follow as our clients are following…??? ( many times we do not have the targeted packaging to study and in glass definitely we are getting good result for fragrance retention.)

    1. Perry Romanowski

      If you don’t have the final packaging you should do a study in something that is close. Maybe the same plastic.

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  68. hassan

    hello my dear master
    this is wonderfull site
    I have a problem for cream oxidante(3%,6%,12%) in my factory, please help me!!
    I want accelator test for cream oxidante current metho or faster than,
    my cream oxidante bubble after produce or in stores after 8 month and many cases throwback to factory? what is the problem ??and when I produce new prototypes, I dont now it will be bubble or not????

  69. Mahnaz

    What is the storage condition (temperature and humidity) for shampoo, toothpaste, soap and hand washing liquid in stores?
    Could you please introduce me a reliable reference?

    1. Perry Romanowski

      Storage conditions are suggested in the blog post.

  70. Rudzani Lynette Makakavhule

    Hi, I’m in the process of starting my owno cosmetics products i would like to know what other tests to do. Apart from .ph, microbial viscous stability colour. What others can i do , which will not need expensive equipment. Please provide methods if possible

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  72. Yemi

    Wonderful wonderful site. I’ve the same problem with multi crystallization point for a plant based butter formula with oils as an earlier writer. Shea to be exact. I really need advice on how to reduce the granularity once it warms up and cools in a relatively warm country (34C day, 15C night) for 8 of 12 months and at its coldest (16C day, 4C at night) for 4 months! Would love advice on how to eliminate graininess… Or resources on same.

    1. NadiaZ

      Dear Yemi,

      I do many products with a high percentage of shea butter. The granularity is a natural property of shea butter especially when unrefined and even if it lower its attractivity on mainstream market, its benefits outweights its cons. There are ways to reduce granularity and stabilize your formula which are mostly based on the use of high temperature waxes such as candella wax or even beeswax. I do not use wax because I consider that it lower the therapeutic property of shea butter, first because you will lower your concentration to put the waxes and second because you will have to heat up your preparation in a way that you loose part of the chemical constituents such as vitamins of shea butter. When you don’t use waxes you need to follow a specific protocol for cristallization with attention to temperature, temperature gradients and storage to keep your formula smooth. But without a complete cold chain there is no way your formula will be stable when reaching the customer as melting can occur in the car or in the shop. So for my products I simply explain to customers how to store properly and simple steps to do to make the product more creamy in case it has become grainy. Besides, as it melts immediately when in contact with the skin, it is really an esthetic quest rather that adding a true value in terms of the skin benefits of the formula. But for sure it requires a customer to be plant friendly and quite aware. Same criticism can come on the smell of unrefined shea butter versus refined (which doesn’t present the same properties) and every oil for that matter. I opt for the most active ingredients and explain to customers that a plant product has its own specificities that one needs to welcome together with its benefits. A plant without plant smell or texture is like eating a strawberry candy and asking why it doesn’t bring you the benefits of a fresh strawberry…
      I recommend you not to store your shea butter preparation for more than 2 years if you wish to keep enough vitamins as well as reduce the potential for UV damage.
      Best regards

  73. Laura


    I need to create for my company a standard test by centrifuge to know if my products are stable or not. Can you help me ?
    Because I am not sure for the testing time and the speed for the centrifuge.


    1. Perry Romanowski

      Most companies do not use centrifuge for stability testing. Why do you want to? In general, you could conduct a standard stability test and run a centrifuge test until you get matching results.

      1. Laura

        My company make standard stability test yet but they want to use a fast test. I know centrifuge test can give fast result about the stability of the formula. In my school we make for centrifuge a 15 min test with 2500 turn/min, but I dont know if there are a standard speed or time?

        1. T. Sobisch

          Dear Laura,

          what counts is the effective acceleration. Duration and acceleration should be adapted to product, i.e. for a lotion shorter duration should work than for a w/o creme. We work with an acceleration of 2300 times earth gravity. For lotions, shampoos often 2 hours is sufficient to rank stability, for cremes we do a measurement over night. When using a shorter measurement it is recommended to do a second measurement at lower acceleration but increasing duration by the factor acceleration is lower. this serves to check for effect of centrifugal acceleration on sample, e.g. Newtonian or shear thinning behaviour.

    2. T. Sobisch

      Dear Laura,

      In my experience centrifuge testing is an option broadly applied, even if not used in every company. For this purpose LUM (my current employer) offers LUMiSizer and LUMiFuge instruments with the advantage being able to directly measure separation during centrifugation instead of visual judgement after centrifugation. Time to run depends on your sample structural stability. For lotions and shampoos 2 hours at 2300 times gravity is usually enough to rank stability for up to 12 samples simultaneously. Check for effect of acceleration at a second lower acceleration for equivalent time should be performed. For creams etc. usually a run over night is necessary.
      For these longer measurements your focus should be on structural stability, to observe whether/how degree of separation changes during storage by comparing with the results for the samples freshen prepared.

  74. Alicia


    So glad I found this website. I am quite concerned as the creams I have made consist mostly of different oils including shea butter. It is really important for these oils to be kept in a cool environment because they all have different melting points. If the temperature fluctuates too drastically they will crystallize, thus affecting the texture. This is already going to be noted on my labels but will this affect anything else in relation to my ability to sell the product? How can I test different temperatures or do I only note the changes in relation to the other factors, omitting the effect it has on the texture? The consistency remains the same over time if the temperature is stable.

    1. Perry Romanowski

      You should really make a formula that can pass stability testing. Not doing so will hurt your performance in the marketplace.

    2. T. Sobisch

      As the texture is effected due to crystallization (and melting, different crystal modifications), which is indeed very tricky, one focus of stability testing should be on measurement of texture alterations. Temperature cycling should be than a meaningful test.

  75. Pingback:Your Cosmetics May Be Contaminated Too | Stephene Bilodeau

  76. Yazan

    Hi Perry,

    I hope you are doing very fine,

    just I sent you to ask you one question, at this moment we are doing some types of sun protection formula, but at 40°C the formulas are not stable, so my question is can you please suggest me what ingredients that can be used to protect the formula at that temperature and higher.

  77. Bindu

    Hi Perry,

    Thanks for such an informative website. If storage temperature for a cosmetic product has been labeled as 4-25c is it sufficient to base it on stability studies done at 25c and accelerated stability of 37c and 45c. Or do you have to subject the product at 4c as well?



    1. Perry Romanowski

      Usually 4C is included as the control.

      1. Bindu

        Hi Perry,

        Thanks for replying. So what happens in a case where the product has not been subjected to 4C studies? Can it still be claimed that the product can be stored at 4-25C?

        1. Perry Romanowski

          Well if you haven’t tested the product at 4C you shouldn’t make the claim that it can be stored at that temperature. It will probably be fine but there may be things in the formula that crystalize at those lower temperatures.

          1. Bindu

            That’s what I thought in regards to making a claim of 4C. Thanks for confirming.

  78. Thi Thi San

    Hi, my product is mosquito repellent containing limonene. I tested the active limonene at 30C and 40C for 12 weeks. After 12 weeks, only 93% of limonene remains in preparation. I want to know active compound % interval in cosmetic. Please kindly reply to me.

    1. Perry Romanowski

      Hello – I do not know what your question means. Could you please rephrase?

      Limonene is an ingredient used in the creation for fragrances and is also a known allergen.

      1. THI THI SAN

        Hi Sir,

        Thank you for ur kind reply.

        Is there any limited range of percentage remaining in the cosmetic preparation during chemical stability test?
        How much percentage of limonene can cause allergy for topical preparation?

  79. SK

    I’m experiencing discoloration (i.e. shifting to a grayish hue from white) in my lotion after the product has been at higher temperatures (50 C) for an extended period of time. Why is this occuring?

    1. Perry Romanowski

      Probably oxidation of something in your fragrance or a chemical reaction between ingredients in your formulas. Without more information it is difficult to say.

  80. Sonita

    Hi Perry,

    Thanks for this valuable information.
    May I have a reference for this storage test ?


    1. Perry

      Much of the information can be found in the following book…

      Magdassi, Shlomo & Elka Touitou edt. “Novel Cosmetic Delivery Systems”, chapter 6, pg 116. Marcel Dekker. New York. 1999.

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  83. jake

    What kind of stability testing would be needed for a new package design, (8oz to 6oz MDPE tube) for a depilatory cream? How long long would that process take and is there a way to speed it up to get the product to market?

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  85. Frank

    I so much like this article about stability test. I have produced some products like shampoo, dishwash liquid, but they are under test. I am from Africa, Nigeria precisely. I have a question. Since Africa has a higher temperature or hot weather, say above 30 C, pls at what temperature do i test my dish wash, shampoo body wash, for shelf life of 1 year. Thanks. Your site is quite helpful..

    1. Perry

      The idea of stability tests is to predict how your product will behave throughout its lifecycle. So, if it normally stays above 30C you should probably stability test at 45-48 C for 12 weeks to predict yearly stability. But this will depend on the formula. Liquids like dish wash and shampoo are fine at those temperatures. Emulsions might not be as predictive when tested like that.

  86. Gian

    Hello Perry

    Great and informative website! Such fantastic knowledge source.
    I would like to ak you about what you think about me using my oven at home to do cosmetic product stability testing at elevated temperature? Is that fine?

    Look forward to hearing from you. Thank you!

    1. Perry

      While you could use an oven, to do a stability test you need to leave the samples in the oven for an extended period of time (say a couple months). I’m not sure if that is something you would want to do.

  87. Jen

    Hi Perry,

    Thank you for putting together such an informative website and discussion forum. I am currently working on a clear body wash with a typical surfactant system, SLES, betaine, etc. that is very salt responsive. We are trying to determine a reasonable viscosity spec that will result in desirable consumer attributes but not too narrow for our production capabilites. My questions are 1. What is a good average?typical viscosity for a clear body wash formula? 2. If our marketing folks want a viscosity around 10,000 then what is the best way to set a range to achieve this most of the time but not constrain our production/quality? Thanks.

    1. Perry

      A good body wash viscosity spec is between 2000 – 7000 cps with a target of 5000. Of course, this depends on the spindle of the viscometer you are using.

      To target 10,000 set a spec of 8500 – 11500.

  88. Haluk

    Thanks for this great website!
    I am new on this topic as well.
    I will store my products a RT, 4C and 45C for 16 weeks to see if they will be good for two years.
    The thing i want to ask, should i wait the samples to reach RT again before i test their pH, viscosity, etc.
    Let’s say, the sample has been at 4C for 2 weeks now. Should i take it out and test when it is at 4C or wait it to reach 25c?
    Thank you.

    1. Perry

      Yes, you should let all the samples equilibrate to RT before testing.

  89. Kirstin

    Hi Perry,

    I would like to know what “advanced” stability testing is available if I only have 1 month to complete it. I will do freeze thawing cycles but was wondering at what temperatures can I conduct my experiments at for thermal testing. I have perfume and nail polish formulations.

    Thank you!

    1. Perry

      If you only have 1 month, you should try 45C storage conditions.

    2. T. Sobisch

      Dear Kristin,

      you may apply a combination with multisample analytical centrifugation. This can be used to trace the very first changes in structural stability very sensitively. Check the stability of the products after preparation and check it after one month storage at RT. You may also trace changes after storage at elevated temperature after some days and after one, two or three freeze-thaw cycles.


  90. Fazlina

    Hi Perry,

    This article and thread has definitely shed some lights about stability testing for me, a rookie. I’m currently formulating a whitening cream based on arbutin and a few other herbal extracts. After 14 days at 45C, the cream in actual packaging (acrylic jar) becomes brownish, while the control (RT) maintains its original white form. There’s no significant changes in the texture, just color. There is 0.6% of tocopherol in the formulation as antioxidant, no UV filter. Any thoughts on why that happen? I’ll be carrying out cycle testing later (24h in 4C, 24h in RT) to see if there is any separation. I hope you could help me out.

    1. Perry

      Well, the tocopherol just might not be a good enough antioxidant and it won’t help if the problem is caused by light. I assume you ran the 45C sample in darkness so light is not a factor? Without knowing more of the formula, any number of things could be causing the browning. You could try a knockout experiment and see if you can isolate what is turning brown, then reduce the level or find a replacement.

    2. Renee

      The Arbutin is the main contributor to the color change in your formulation. Make a control sample omitting the Arbutin.

  91. AC

    Hi Perry

    Many thanks for putting up this website, so informative. I just have a very specific question though about stability. About the pH of a product that is at 25deg C RT, 25deg C dayligt, and 37 deg C, what can you say about a product that after 2-week timepoint, the pH dropped by 0.50 unit? Say, from pH 5.50 to 5.00. Is this a common situation or does this indicate an instability in the product?

    Looking forward to hearing from you. Many thanks

    1. Perry

      Hello AC – thanks for the kind words.

      For your specific product it is too early to tell whether that is a significant enough change. It also depends on your pH specification. If the pH spec is 5.5 – 6.5 then you might have a problem. But if the spec range is 5.0 – 6.0 then probably not. And if the spec range is 4.5 – 5.5 then you definitely don’t have a problem.

      1. AC

        Hi Perry

        Many thanks for your response. Followup question, does that mean then that for as long as the pH (let’s say after 12-week period) is still within the specification set (whether bordering the minimum or is exactly at the minimum), then that product may still be considered to have passed the test? I will be more specific with the storage condition, let’s say that is the situation for a 25 deg C RT and 25 deg C daylight. And will it also be the same if the sample is the one stored at 37 deg C?

        Another question would be, let’s say after a 12-week period, all samples’ pH (4deg C, 25 deg RT, 25 deg daylight and 37 deg), have dropped by 0.50 to 1.0 unit but still within the specification (only bordering or at the minimum range), can the product/formulation be said to still have passed the test? I am not sure whether the extent or percentage drop in the pH is playing a key role in passing or failing the stability test for a product. And whether or not this doesn’t really matter for as long as the final pH of the samples at different storage condition after the 12-week stability test are still within the set specification.

        Many thanks again Perry and thanks in advance for your answet to this these questions.

        Kind regards

        1. Perry

          Of course, this depends on your company but yes, it is reasonable to say that if the pH stays within a specific range, than the product is stable even if the pH changes a bit (even 0.5 – 1.0 units).

          1. EM

            Aren’t those specific rages decided by the formulator himself?
            I did the stability test for a cream at accelerated conditions (4 months) and I noticed a drop of pH with 1.5 units (from 7 to 5.5). I have noticed the pH drop at an other cream with the same ingredients but higher % (different formula), but the drop was with 1 unit (3 months of accelerated conditions, from 7 to 6) At this point, I will put the pH range 5-7 for the first cream and 5.5-7.5 for the other one. With all this said, I decided at the end the pH range based on the stability test.

          2. Perry Romanowski

            Yes, the ranges are set by the formulator. But they also are adjusted to reflect real-life production data.

  92. BEERAM

    Dear sir,

    Am a research associate in formulation and development, i need complete information regarding cosmetics stability studies like FREEZE THAW & CYCLING how many months we have to keep for stability. please help me on this sir.
    Thanking you.


    1. Perry

      All the information you need is in this post or in another stability testing post on this website. Do a search.

  93. P

    Hi ,

    After reading many “Make Your Own Toiletries” info online, this info here is one of the best! Tks!

    As one of the “Make Your Own Toiletries” owner of a small business, my question is, how do you determine the expiry date of a batch of lotion?
    Ready made lotion + frag/essential oil + colour

    1. Perry

      To determine the expiration date, you have to do a stability test.

  94. nina

    I was contacted by whole foods regarding my body scrubs they are interested in carrying in their stores. They have asked me to provide them with stability tests of my scrubs. Would I be able to use the one that you discuss above? Any other suggestions? Also, what does RT, 40C, etc…stand for??

    Thanks for your help,


    1. Perry


      Congratulations! That’s a big accomplishment to get into their stores.

      Yes, you can use the procedure outlined in this stability testing post. Those numbers/letters indicate temperatures. Those are the storage conditions you are supposed to keep your samples at for various periods of time.

      RT = Room Temperature
      40C = 40 degrees Centigrade

  95. Maria

    Hi Perry,
    How often do we do microbiological testing and for how long do we need to do it when conducting stability studies of cosmetics, lotions in particular?

    Thanks a lot. You’ve been very helpful.

    1. Perry

      Micro challenge testing should be done right at the start, then again on a sample that has been stored for 8 weeks at 45C. If it holds up to those conditions you can feel pretty confident in stability.

      1. Maria

        Thanks, Perry. I know that test need to be done at the start of studies but I was not sure how far or how often to do it. Now I know. Thanks again.

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  97. Nina Caisido

    I would like to share the Q-rule, on my understanding, it can be applied to cosmetics as well. A sample computation will be: when product is stored at 45°C at 3 months, T = 27 months @ 25°C, so if you want to change the storage condition or temperature, just use the formula T = t x (Q10)n .. you may want to check the link for a detailed explanation..

    1. Perry

      Thanks Nina! Very helpful.

      1. Nina Caisido

        Glad that I was able to share.. because I can see that some are missing the fact that we belong to different regions and the definition of room temperature varies. As for us in the Philippines, RT is rarely 25°C. And I can say that it is safe to use RT at 30°C, therefore conducting accelerated stability for 3 months at 45°C, can only give an estimated shelf life of 9 months at RT. In order to have at least 24 months shelf life, stability studies should at least be conducted at 4.5months @ 45°C. Thank you for all your help, Perry! More power!! 🙂

  98. Fleury Mathias

    It is also noticeable that commercially available instruments enable the determination of cosmetics stability in a shorter time period, thanks to optical measurement (Multiple Light Scattering for instance), such as the Turbiscan (Formulaction).

  99. Diana

    Hello Perry,
    Thank You for informative article!

    Our company creates fragrances for different functional means.
    For cosmetic formulas we use procedures similar with mentioned in your article.
    Could you recommend some methods (literature, references) for verification a fragrance’s stability in chlorine-containing bases, in alkaline cleaners?

  100. ulhas

    hi perry
    how analysts do colour matching in qc lab ? i want information about analytical method and procedure plllllllllllzzzz?

    1. Perry

      Well, typically you use a standard control and compare the samples. You can also use a color matching card but a sample is better.

  101. Jorge

    Can you elaborate on the 45C for 8 weeks? What data validate? Do you recommmend for bith chemical and microbiological accelerated stability testing?

    1. Perry

      I don’t understand your question. 45C for 8 weeks is supposed to be predictive of what RT for 1 year would be. It’s not a perfect model but it’s pretty good and good enough for most cosmetic formulas. Data that validates would be pH, Viscosity, color, and odor. Also, you should do 8 weeks micro challenge testing

  102. Kim Smith

    I was wondering how important is testing in the 50c? We have a petrolautum base product with color in it and at 50c it seperates. Should we be concerned with this? Would the 45c test be enough?

    1. Perry

      50C is really higher than you need however it does depend on the conditions which your product will ultimately be shipped in. If you sell a lot in Arizona during the sumnmer then it is going to need to be stable at 50C. But for most products, 45C would be enough.

  103. Stephanie

    Hi Perry!

    Thanks for the great write up.

    “A handy rule of thumb is that a sample stored at 45C for 8 weeks is equivalent to one that is stored at room temperature for one year. This isn’t an exact predictor, but is good enough for the purposes of cosmetic products.”

    Would I be correct to assume that this statement is based on the Arrhenius equation? Where an increase of 10C in temperature doubles the rate of a reaction?

    I was wondering if you could point me to some journals/articles that mention this? I’m currently doing my write up for my thesis and am not able to find any references for that statement.

    Your help would be greatly appreciated. Thanks in advance!


    1. Perry

      Hello Stephanie,

      Indeed, I believe it was derived from the Arrhenius equation. I’m not sure of exact references but you can check the following for more information.

      1. Eccleston GM. Application of emulsion stability theories to mobile and semisolid O/W emulsions. Cosmetics & Toiletries 1986: 101(11): 73-135
      2. Rieger M. Stability testing of macroemulsions. Cosmetics & Toiletries 1991; 106(5): 59-66
      3. Garrett, E.R. Prediction of stability of drugs and pharmaceutical preparations. J. Pharm. Sci., 1962, 51, 811-833

      Hope that helps

      1. Stephanie

        Will check it out!

        Thanks, Perry! 🙂

    2. T. Sobisch

      Dear Stephanie,

      you have to distinct between microbial/chemical stability and separation stability. Arrhenius applies to the first but not to the second. So in my view it is purely empirical and applies more or less. Temperature effect on separation stability is manyfold mainly influencing viscosity (creaming), Ostwald ripening through diffusion/solubility and effect of temperature on emulsifier polarity and phase diagrams.


  104. Zoheb

    Hi Perry,

    Very informative article, I am a student of pharmacy and our teacher asked us that “In ICH guidelines storage condition in stability testing why is it so that we keep product at 25,30,40 degrees C for 12,6,6 months respectively?” I mean she asked why these specific timings only why not less or more. Can you help me please.

    Thanks in advance

    1. Perry

      Hello Zoheb,

      I’m not certain of this answer but this is my guess.

      1. The reason you have samples at 25C for 12 months is because one year stability at room temperature is the standard goal. Going for less time at room temperature will give you no indication of how stable a product will be at one year.

      2. The reason to go 30C for 6 months is because it is generally believed that this accelerated conditions will predict what will happen to the sample if it was held at RT for 1 year. Higher temperatures initiate chemical reactions that may have occurred over time.

      3. The reason to go 40C for 6 months is the same as the 30C except for 40C, it will be predictive of 1 year stability after 3 months. If you go for 6 months it will be predictive of stability for 2 years.

      That would be my guess.

      1. Zoheb

        Thank you very much perry.

  105. T. Sobisch

    I broad up a discussion in SpecialChem4Cosmetics to several related Groups of LinkedIn.
    The discussions show up a broad range of different approaches.
    here the links

  106. rupali

    sir, we are manufacture of shampoo, but we face a lots of problem in viscosity ,can you guide me which precaution take during shampoo manufacturing for viscosity? and is it effect of flow rate or addition speed and stirring tme and speed of raw material on viscosity?
    thanks and regards

    1. Perry

      @Rupali – your question is much too broad to provide a simple answer. The main things that affect shampoo viscosity include Salt %, surfactant type, and thickener. As long as you have good mixing, things like speed of mixing and stirring time doesn’t have much effect. Of course, this could be the case depending on the specific formula type.

      1. rupali katkar

        Hi peery,
        thanks for answer, can you suggest me any book which i refer for viscsity because i want deep study in viscosity of product.

        Thank you and regard

        1. Perry

          I’d suggest you pose the question in the cosmetic science forum. You might get some better answers. Search for more articles on this site too.

  107. Hamlet

    Hi Perry,

    Thank you for this informative and helpful website. I am currently handling a shelf life extension project from 36 months to 48 months. I would like to ask if what micro test should I do for my accelerated study, is it the micro contamination test? Is 12 months 40 deg C enough to simulate 48 months shelf life? Thank you in advance!

  108. Lucie


    Thank you for this nice summary on stability. I was wondering if the cosmetic industry is testing the stability of the chemical itself? The formulation can be stable if we consider the physical state, the pH, no color, no odor… but if the active ingredient that we put in is not stable what is happening? Does cosmetic industry is following the chemical stability in the formula with appropriate methods? Thank you 🙂

    1. Perry

      For cosmetics, the “active” ingredients are rarely tested for stability. Sometimes performance tests are done on stability samples to ensure that the product still works however, this isn’t usually the case. The assumption is that if the samples pass the stability specifications then it will still work. For OTC products like Sunscreens, Anti-dandruff shampoos, and Anti-perspirants, performance testing is a requirement of stability testing.

      1. Thi Thi San

        May I know the analysing data on a quantitative attribute that is expected in cosmetic product to change with time. For eg API in drug is recognized as 95%.

        1. Perry Romanowski

          There are no such quantitative standards in the cosmetic industry. It is dependent on the standards of the company you work for.


    Hi. I have a question on the retest period and shelf life of the product. My understanding is it is loosely based on the which essentially says that These two are different. for any of the marketed product shall we give the retest period instead of the shelf life. if it is possible let me know what the company’s product is there in market with retest period.
    Your comments, thanks.

  110. Sujatha

    Hello sir,

    Thank you so much for posting informative posts. I am working as a formulator in a cosmetic industry. Basically i came from pharma background but I have an interest in developing new cosmetic formulas. Recently I have developed a shampoo formula which is in stability studies. Can you please give me your mail ID so that i can clarify my doubts which are arising during the development of formula.

  111. pvexplore

    On a general note, Is it required for cosmetics to still undergo “long-term” stability testing? or just the accelerated stability is enough. Thanks!

    1. Perry

      This depends on how your company feels about the subject. Long term stability testing is the standard. When you do accelerated testing you could possibly miss some stability failures. It all depends on what level of risk you want to take. There are no set rules.

  112. Perry

    Thanks Diana!

    This really depends on the type of shampoo and the position of the brand. But typically shampoos will have viscosity ranges from 5000 cps – 20,000 cps (lv3, 12 rpm)

    1. rupali katkar

      sir, we are manufacture of shampoo, but we face a lots of problem in viscosity ,can you guide me which precaution take during shampoo manufacturing for viscosity? and is it effect of flow rate or addition speed and stirring tme and speed of raw material on viscosity?

  113. Diana Bernard

    Hi Perry,

    Love your website, and the on-line education!
    What is the average viscosity rating for professional shampoos?


  114. Gi

    Hi! Your site is so informative and easy to follow. Im also wondering: How can i perform microbiological test on lipsticks that I’m evaluating? Any idea on what culture media to use and other parameters to watch?

  115. Diana Bernard

    Hi Perry,

    Thanks for the info, will try out your recommendations…

    Take care,


  116. Perry

    @Diana – The proteins could become more yellow upon exposure to heat and time. So, you could reduce the level of those ingredients. They likely don’t have much effect on product performance. You can verify it yourself by creating the product with and without the ingredients and see if you can tell any difference. Note: you should do this test in a blinded fashion so your results are unbiased.

    The other thing you can try is to add an antioxidant (like benzophenone). This may help.

    Finally, if you have a fragrance in the product this could lead to yellowing. In this case, you might have to have the fragrance house reformulate the fragrance.

  117. Diana Bernard

    We are making a shampoo, and have collagen, keratin and vegetable proteins in the formula, and we can’t get the formula a nice white color, keeps getting yellow….
    Any suggestions?

  118. whopper

    can anyone help me with stability testing of tooth paste and mouth washes.

    1. rupali katkar

      sir, can you sugesest me, which parameter are check in acerlative stability study of toothpaste?

  119. Simona Neamtu

    Hi Perry,

    Your information helps me, but I want to know the legal document (Cosmetic Directive, Colipa Guidelines, etc. or other documents)on which you based because we want to do this test.
    Thank you,

  120. derek Herrmann

    Hi Perry,

    Well when you do pack testing to ensure the product is stable in the given packaging, tube, tottle, bottle, plastic jar etc, what do you check for how do you control it!? Something i have always found hard to find a good test method as obviously sometimes the product can cause advers reaction to the pack, essential oils for example!
    Hope this makes sense and look froward to your reply…..

  121. Perry

    @Derek – What exactly are you looking for?

  122. Derek herrmann

    Could you give me advice on pack testing so the product in the packaging!?

    1. R.Swaminathan

      Dear Sir
      Selection of Packing Materials to suit the product and its stability- my views- if you want to pack surfactant base product – shampoo, Hand wash , Face wash etc in a plastic container- you should know the stability of the container . To check the suitability – you have to add 50 ml. of 10% Non-Ionic surfactant – 9 to 10 mole in to the container and keep at 45 deg.c oven for about one week . check any crack formation. If yes- advise your plastic supplier to add few % 0.2 to 0.5% EVA in to it and proceed the same test. Your container will pass.

      In the case of cream in tube- to find out Seamless or Lami or Alu.layered Lami tube- no issue- fill the product in to the tube and do some disturbance with fingers for about one minutes. Open and see the product consistency . Based on the product consistency – you can select the PM.

      For printed tubes- if you want to check the print stability – no issue- you can check tap stability test. One more study- apply the product on the printed portion and leave for 24 hours. Check the print stability and check with tube supplier for getting right tubes.

      Product Stability: In the case of Toilet cleaner- Acid base- some time many customers are facing separation problem after 3 or 6 months ( 1 batch out of 100 -it may happen) . No issue- you can know the status – the day of manufacturing. Very simple- take about 50ml. of toilet cleaner in a glass beaker and heat to 100 deg.c and cool it immediately. if you are noticing separation – surely your product will be separation after few months. Reason for separation- some iron metals contamination with product. I hope – will be useful.

  123. Perry

    @Aija – You put samples at 5C, RT and 40C. You can make a decision to proceed if it passes 40C stability for 8 weeks. Some companies like to go for 12 weeks but this isn’t always necessary.

    @Madie – Thanks for the kind words!

  124. Aija

    How do you test a fragrance stability? Do you keep the product in 5 C, room and 40 C temperature? For how long you do it?

  125. madie zoe

    Your site is very informative!I’m currently making a public lecture presentation on safety standards for cosmetics and am planning to perform comparative stability testing for different commercial cosmetic products for my research , if approved. Thank you for the inspiration!

  126. Perry

    Hello Mayur – again it depends on the reagent but if something is stable at 37C for a week, I would anticipate it would be stable at 2-8C for at least a month.

  127. Mayur

    Hi! Perry! Thanks for ur comment.. But i wana know if i expose my reagent at 37*C for a week, n if they are stable, then what would be its life at 2-8*C?

  128. mariana

    Hi, i want to more information about the good form of stability test.

    Best regards

  129. Perry

    @Mayur – you can’t really give a specific number and each formulation is different. A rough guide is that 45C at 8 weeks is equivalent to 1 year at room temperature.

  130. Mayur

    This article is really informative. Thanks for that. I had understand the basics steps. If I expose my reagent at 45*c for 2 weeks or something,naturally they start degrading. Now I want to know for how many days my reagent is going to survive? Means I want to had to have numerical figure like 240 days or something is the figure during which this reagent will work and after that its going to be expire.. So please let me know. This will really help me in my study.. Thank you very much in advance.

  131. Aija

    What could be the stability test for facial toner? pH and microbiological tests, of course. What temperature and how long to keep the sample in this temperature?
    Does it really make changes if for the freeze-thaw test I use refrigerator where temperature is -18C?
    And what to do, if the shampoo after some weeks became a little more liquid. I can add some more thickening agent. It is hard to work with natural cosmetic, because we can’t use some very effective but synthetic ingredients.

    1. Perry

      I would use the same temperatures suggested in this post to test a facial toner. As long as the temperature of the refrigerator goes below the freezing point, you can use it for stability testing.

  132. Sonia Zabal

    I would like a sample how to calculate the stability of a product using the Arrhenius equation (Q10).
    A practical sample .As our Ministry of Health needs us to submit such an application for each Cosmetic Product

  133. Perry

    @Cindy – It really depends on what product you are trying to make. If it is a lotion, shampoo, body wash or something like that, you can use food coloring. If it is makeup, then you need to use Iron Oxide. The way to handle that is to premix the iron oxide in another material before adding to the water.

  134. cindy

    Hi Perry would like to ask you about colorants..
    I am using powder iron oxide on a very simple formula… but it is toooooo clumpy when mixed with water… what other colorants (liquid) can I use . and will they use less % to achieve the same amount as a powder. I am trying to keep my formua %’s down so as to use my main ingredient % more. I am not a chemist, just a consumer who wants a better product for myself and others. I need a little advise before turning it over to a manufacturing chemist. Thanks

  135. Allen

    Hi. I have a question on the extrapolation of accelerated stability data. My understanding is it is loosely based on the Arrhenius equation which essentially says that for every 10 deg C increase in temperature there is a doubling in the reaction rate. So, if you RT testing is done at 20 deg C and your accelerated is at 40 deg C, this would give you a quadruple reaction rate, that is a 3 month accelerated stability at 40 deg C would be equivalent to 1 year at RT stability. Your comments, thanks.

    1. Perry

      @Allen – Yeah, that’s about right. Our RT stability was done at a slightly higher temperature (~25C) so we always used 45C at 3 months as equivalent to 1 year RT. But stability testing is not an exact science so 40C for 3 months may be good enough.

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  137. David Steinberg

    I always wonder about this complex subject. I was an expert witness in a lawsuit where a drug at RT had 6 + years stability but failed the USP test. Interesting court testimony on both sides.

    Anyway, the real reason for my comment is the EU. They require a PAO (period after opening) symbol with a number and a capitol M to indicate how many months “after the product is opened by the consumer, it will not cause the consumer harm”. This is required for all cosmetics with over 30 months stability. I won’t get into to complexity of what “causing harm” means or the new PAO regulations effective 2013.

    My question is: why doesn’t the EU establish a test for 30 months stability?

  138. Derek Herrmann


    could you describe the tests you do for packaging stability and the protocols involved!?

  139. Emiro

    Hello friends
    Follow the link to the guideline that we are using in Brazil like basic reference to test the stability of cosmetic products. Is in English.

  140. LINA

    I completed my thesis work i done M.Tech in cosmetics i want to know about my sample (cream) shelf life of product .I check the stability of my sample for 1 month .Then my question is what is the shelf life of my product.

    1. Perry

      @Lina – Typically, 4 weeks of stability testing at elevated temps will be indicative of about 6 months of stability. 8 weeks can predict 1 year.


    stability studies for all cosmetics products are similar or different (sampoo ,creams ,lipistics etc) ?

    1. Perry

      @Dhaniram – in general they are the same. Put samples at various conditions and measure specific properties. The conditions are the same. The specific measurements will change depending on the type of product you are testing.

  142. Jonathan

    Only recommended tempteratures were given in you article. Do you also control humidity in stability studies?

    1. Perry

      Control of humidity is generally not considered when doing a normal stability test. But there are times (depending on the type of product) where humidity control would matter.

  143. shweta shekokar

    Dear Sir,
    i am facing problem in shampoo. our shampoo are getting liquid and getting high micro counts in our batches. this is happening within 15 days or with in a weeks time of manufacturing date. to inform you that we have a check at every step of production i.e from missuing raw material to the final batch then also the problem is persistent . the main thing is all batches are fresh .

    pls do Reply.
    Thank you

    1. Perry

      @Sweta – it’s difficult to say but it sounds like one of two possibilities.

      1. You’ve got a micro contamination problem in your production lines
      2. You do not have an adequate preservative system in your shampoo

  144. Diana Bernard

    Hi Perry,
    Thanks for your quick response, I’m so glad I found your website, lots of valuable info. What’s your email address, and I”ll send you the ingredient list, to send the formula would take a few days, not at that location. Also, I’m interested in your training program, when does the next one start?

  145. Diana Bernard

    We are developing a shampoo line. It took about 6 months to come up with a formula that we really like. We have encountered two issues:
    1. The formula seems to decrease in thickness about 50% after one month in the bottle
    2. Can’t seems to re-create the exact formula again, i.e., color is different, not performing like the formula that thinned out
    Can you give us any suggestions to our problems?

    1. Perry

      @Diana – it’s difficult to offer suggestions without knowing more about the formula. So, if you want to email me separately the formula (or at least the ingredient list), I can offer a better opinion.

      For the color problem, you’ll just have to do some color matching and keep track of the amount of dye added.

  146. Constantinos

    If i want to measure shelf life of a hand soap,45C for 8 weeks is equivalent with one year?This means that 16 weeks are equal with two years?

    1. Perry

      @constantinos – That would be a reasonable assumption. Although, the farther out in time you go, the less reliable the prediction.

  147. Lisa

    Is there an article or handbook that this rule of thumb comes from?

    1. Perry

      @Lisa – not really. It’s just an industry standard.

  148. David

    For a three year expiration date on an OTC product, say a sunscreen or OTC analgesic in cream form, what would the acceptable accelerated program look like? 45 degrees C for how many months? (as well as RT, FT, 25 and 40 degrees C).

    Does 3 months at 45 degrees C. ever equal a three year shelf life for a sunscreen?


    1. Perry

      @David – The only acceptable accelerated stability for the FDA is the following (according to the sunscreen monograph). If you want to make a 3 year expiration date claim, you have to conduct stability testing for 1 year. If you want to make a 1 year shelf life claim, stability testing for 3 months is acceptable.

  149. Perry

    @Mitch – I don’t have one at the moment but will try to create one for a future post.

  150. mitch

    Do any of you a sample form showing how to lay out your study?

  151. Perry

    @Jen – if the surfactant system contains particles like an opacifier / pearling agent, then it wouldn’t be surprising to see a change in viscosity. But a drastic change as you’ve indicated in a simple surfactant solution could be a stability problem. However, you should not make stability decisions based solely on the 50C sample. Wait a little longer and see what happens with the 45C or 37C samples.

    1. Sandy

      I am using a liquid pearl blend for body wash and getting separation (clear layer on bottom) in 45C stability testing. Is this really indicative of room temperature performance? I don’t see it when comparing to RT stored samples – >1 year old. Is there an explanation for this. I’m thinking when viscosity drops with heat, pearlizer falls out; but wouldn’t do so without heat.


  152. Jen Smith

    Would you expect significant changes in viscosity at 50 C due to the harsh condition or would you say that it is indicative of an unstable formula? For instance, a decrease in viscosity from 23,000 cps to 12,000 cps in a surfactant system.

  153. Jen Smith

    This website is very helpful. What about accelerated stability at 50C? How does this translate to real time?


    1. Perry

      At 50C, you create some chemical/physical changes that wouldn’t happen at room temperature so it’s not so easy to give a direct time relationship between 50C and room temperature. But if you want a number, 50C for 2 weeks would be about 3 months at room temperature.

  154. Pallavi

    The article given above is quite informative.Thanks for such an article.I wanted to know the accelerated stability testing of perfumes in cosmetic formulations.What procedure can we follow for the same.

    1. Perry

      You can use the same procedure for a fragrance stability test.

    2. Yu Hsin

      How to test pH value of w/o emulsion?Cause the range of pH is unstable.How can I read the value? Thank you~


    What is the stability testing procedure for a Baby wet wipes. Is there any specific guideline available.

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  157. Sara Marion

    I am someone who needed cosmetics becuase of fibromylagia attacks and was very sensitive to interior windcasting between the years of 2004 to 2008. Since being diagnosed with a disability this year I have had to use a home concoction that I would like to have tested for final ingredients. Is their any help to warrant a working cosmetic product that is not commercially manufactured?

    sara l. marion
    cincinnati, ohio

  158. Ari

    How prediction of shelf life in powder product(compact powder/two way cake),eye shadow and mascara product?thanks a lot

  159. Sean

    I would like to than you for your article above. It’s very informative. Is it possible that the shelf life prediction from accelerated stability study differs for different type of cosmetic products? Unlike Pharmaceutical Products, at the moment there’s no clear-cut guidelines for the prediction of shelf life of Cosmetic Products from the result of the accelerated stability study. I had talked to many formulators, and was told that 3 months of accelerated study is equivalent to 3 years of shelf life at room temperature (unlike what you had mentioned – 6 months). I had also found out that ISO 11609 (1995) (Section 5.4 Determination of Stability) had indicate that: “The toothpaste shall meet the requirements of this International Standard after storage at 40 deg C for 3 months under such conditions of time and temperature as will simulate at room temperature for 30 months.” The above quote was taken from the ISO which is meant especially for the toothpaste. Do you have any idea that is there a separate guideline for a particular type of Cosmetic Products i.e shampoos, body baths, lotions etc.? I’ve been searching for the answer for quite some time, I would really appreciate it if you can enlighten me. Thank you.

    1. Perry

      @Sean – Yes, the predicted shelf life would differ for different products. In general, products like shampoo will last much longer than emulsion based products. Accelerated stability tests are more predictive for non-emulsion products.

      I didn’t mention 3 months = 6 months. We always used 45C for 8 weeks to be equivalent to one year of room temperature storage.

      There is no specific guideline that I am familiar with for any standard shampoo, body wash, lotion, etc. The FDA has some guidelines for OTC products like sunscreens and dandruff shampoos but those are more related to the active ingredients.

  160. Kenneth

    We generally run an accelerated study at 4C (Control) & 50C for 3day, 1wk & 2 wk review, (Any longer than 2 weeks at this temp, I believe will overcook the product) depending on what type of product (e.g. Oil, Alc, Lotion etc.) For F/T testing we gernerally run 3 cycles (In/out, in/out, in/out) and monitor for any precipation or particles falling out of the product.

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  162. dede

    How about the freeze thaw cycle test? how to predict the stability of product whether stable or not?

  163. Shawn Brown

    This is very informative info for anyone who is just getting their feet wet in our industry. This is a pretty through break down. Thank You Perry!

  164. Myriam Vazquez

    One of the more common questions when you are talking about stabilities are: How do I run a an accelerated stability test?And how much shelf life this stability will represent? How do i do a correlation between the time I have on stability and real days.

    1. Perry

      Accelerated stability tests just involve storing samples at higher temperatures.

      A rough estimate accepted in the cosmetic industry is this.

      8 weeks at 45C is equivalent to one year stored at Room Temperature

      This isn’t perfect but typically if your sample stays stable for 8 weeks at 45C, it’ll be good under normal consumer storage for a year.

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