Cosmetic Microbiologist Here. I Can Help Answer Your Germ Questions

edited December 2013 in General
Hi Everybody,

My name is Ben Tanner and I am the microbiologist in charge of Cosmetic Test Labs in Texas.  My lab specializes in cosmetic microbiology, such as preservative challenge tests and aerobic plate counts. 

I was on the old forum for some time as "CosmeticTestLabs."  Anyway, I think there is a great group of people on this forum and so I like to share my microbiological expertise when I can.  Feel free to ask me any germ/preservation/contamination/infection/test questions you might have.  I usually check in every few days.

Happy formulating and testing!

- Ben

For testing help visit us at Cosmetic Test Labs


  • MicroformulationMicroformulation Member, Professional Chemist
    Welcome Back Ben! By the way I have sent some clients your way (can't say which due to NDA) and each one has had a positive experience. Microformulation Cosmetic Consulting provides Custom Formulations for both large Commercial accounts as well as smaller entrepreneurs. We can provide Naturally compliant Formulations under the NSF, NPA, Whole Foods and USDA Organic Certifications. BS.Pharm Albany College of Pharmacy, Union University.
  • MakingSkincareMakingSkincare Member, Professional formulator
    edited December 2013
    Hi Ben

    Welcome back to the forum.  Thanks for offering to help - I would love to have your views on some points made in this article - specifically.....

    Benzyl alcohol and phenoxyethanol should not be formulated with non-ionic surfactants eg polysorbate 80. They will interact and such interactions may not involve conventional chemical transformation, but concern more subtle phenomena e.g. hydrogen bonding and complex formation. Thus the overall level of preservative in the product may not change, but unless the preservative is available in the “free” form its efficacy may be compromised.

    The article also states:-

    EDTA can interact with benzoic acid ....and..

    Adsorption onto excipients, especially those with large surface areas or on to container / closure systems can also remove preservative(s) from solution for example
    - benzoic acid by kaolin
    - phenoxyethanol by pvc plastic, cellulose based excipients
    - sorbic acid/sorbates by plastics (polyproylene, PVC and polyethylene)

    The antimicrobial efficacy of phenoxyethanol is reduced in the presence of the cellulosic suspending agents such as HPMC.

    I'm wondering what your experiences are with the above and whether you agree with points raised in the article?
    Jane Barber (free online course)
    Formulation discussion forum (18,000 members):
  • Welcome back, Ben :)
  • Chemist77Chemist77 Member, PCF student
    @MakingSkincare I have read the link you have posted, I would like to ask if a non-ionic emulsion too renders the preservative ineffective e.g. my emulsion has fatty alcohols, glyceryl stearate and some ester oils. I am not using PS 80.
  • Wow, what a nice welcome back to the forum!  Thanks everybody, and thanks Mark for the referrals.  We have sent some folks your way, too.  Hopefully they have found you well.

    MakingSkinCare - That article is a gem.  I looked over it briefly and will read it in full later.  In the meantime, I can confirm that polysorbate 80 does neutralize certain classes of preservatives.  In fact, we use it in our all-purpose neutralizing broth for that very purpose in the lab.  Here is the product insert and formula if you are interested.  In that document (and in lots of scientific literature), it says the purpose of polysorbate 80 is to neutralize substituted phenolics.  I don't think phenoxyethanol is technically a substituted phenolic (it would seem to me to be more like a monophenyl ether), but it is structurally similar to many substituted phenolics so the two chemicals probably should not be present in the same cosmetic product if the goal is to make it microbiologically stable.

    I am not as familiar with adsorption of preservatives onto plastics, though I know some long-time formulators who consider the plastic type of their packaging to be effectively one more formulation variable.

    As for the cellulosics, I would anticipate some interference with preservative effectiveness, but in a minor way.  We see this with almost all thickening agents.  Maybe the best example comes from a contact lens solution maker several years ago.  I don't have all the information, but I think that basically what happened in that instance is they added a thickening agent to their lens solution to aid in eye feel that bound up some portion of their preservative, thereby knocking out some efficacy and allowing some pathogenic fungi to gain a foothold. 

    Most antimicrobial agents carry a positive charge - and this is just a broad theory of mine - which physically leads them to the negatively charged cell wall, where the rest of the molecule does the destruction.  Since cellulose is a huge molecule with lots of charge variation over its surface, it would not surprise me to see it bind up some preservatives. However I would not expect them to be too tightly bound so the effect may not be a formula-killer.

    milliachemist - some non-ionic surfactants do interfere with antimicrobial efficacy but usually in a minor way and the effect can be expected to vary depending on other aspects of the formulation such as pH.  I don't have a list in my head of which ones should be avoided, but I have definitely seen instances where removal, substitution, or scale-down of a non-ionic surfactant improves antimicrobial activity.

    For testing help visit us at Cosmetic Test Labs
  • Chemist77Chemist77 Member, PCF student
    Great one Ben, thanks once agsin for a perfect 10.
  • MakingSkincareMakingSkincare Member, Professional formulator
    edited June 2014
    Thanks so much Ben.  

    Preservation is such a complex and fascinating area (I'm confessing to being a bit of preservative nerd!).  I've written reviews on commonly used preservatives and am always looking for more info.  I've got a few more questions - I'll just concentrate on the key ones here and if it's OK I will message you a couple of other questions, since I don't want to hog your post.

    Does polysorbate 60 also neutralize substituted phenolics?  A lot of people in my group use ewax which contains it.

    The questions below, are obviously formula dependent...

    what would be your overall opinion of naticide or leucidal liquid (incl the SF version)? I have been cautious not to recommend them as I have not seen independent studies on their effectiveness. 

    Thanks again Ben for your kind help. 
    Jane Barber (free online course)
    Formulation discussion forum (18,000 members):
  • Hi Ben,

    I actually just received a bid from Cosmetic Test Labs to do my testings I need done for my products! So I may be working with you guys real soon. :-) 

    Anyway I have a question about what preservative would be the best fit for "natural" product lines. I know, I prefer not to use "natural" because it means nothing, but it's the best way to sum it up...from the earth, plant-based, not synthetic, no parabens.

    Would a combo of Grapefruit Seed Extract, Citric Acid and Vitamin E be sufficient for a formula that is about 90% water based ingredients (aloe juice, Lime Hydrosol) and 10% oils? A couple of the other ingredients also say they have "mild preservatives" properties to them. If this wouldn't be enough to ensure my products are safe, what do you recommend to fit the needs/wants of my product line?

    Thank you so much in advance for your knowledge in this area. It is much appreciated. :-)
  • Hi MakingSkinCare and Tasiashton,

    Perhaps I can kill two birds with one stone with this statement about "natural" preservatives (including Leucidal):

    Can a cosmetic formulation be microbiologically stabilized using one or more "natural" preservatives like Leucidal, sorbic acid, and lactic acid?  Yes.  Is it easy?  No!  Is it cheap?  No!  Will it always work with "tough" formulations? No!

    And about grapefruit seed extract and vitamin E, I have never been wowed by them.  That's not to say they don't work, just that I don't recall ever seeing it happen, and I vaguely recall some scandal where grapefruit seed extract appeared to have been spiked with quaternary ammonium compounds.

    We get a lot of samples through the lab for preservative challenge testing, many from customers we haven't worked with before who are submitting formulations to us that are as new to them as they are to us.  When they use traditional preservatives (even retailer-preferable traditional preservatives like phenoxyethanol), their success rate on challenge tests is very high.  I estimate they fail only one in every 5 or 10 tests.  That's great, because challenge tests take a long time to conduct and are relatively spendy. 

    On the other hand, when they use natural preservatives it often takes a few rounds of testing and reformulation for them to pass.  That's good for the lab but bad for them, and my heart goes out to them when I see them give up altogether rather than throw in a tiny amount of synthetic preservative and go to market :(  

    So have I seen Leucidal work, yes.  Do I think it is as efficacious as most of the traditional preservatives, no.  But on the other hand, many traditional preservatives are being unfairly vilified.  So unfair or not, there's a great big and trendy marketing trade-off to be considered.

    Frequently we see customers use antifungal preservatives such as sorbic acid in combination with Leucidal.  That seems to be a pretty good place to start and I'm sure the folks at Active Micro Technologies (makers of Luecidal) could give some other suggestions, too.

    MakingSkinCare:  As for polysorbate 60, I doubt it interferes but am not certain.  As for the proposed formulation 1% GC/D GMCY and p-Anisic/Dermostoft, I just don't know.  I am pretty sure that your formulation expertise - even as related to preservation - exceeds mine!  I am a "test it and let's see" sort of guy, which I suppose is a good fit for a testing lab owner :)

    Tasiaashton:  Thanks for giving us a shot!

    Thanks all for the great discussions.
    For testing help visit us at Cosmetic Test Labs
  • MicroformulationMicroformulation Member, Professional Chemist
    Ben, Great post! My opinion on Natural preservatives is right in line with yours.

    Robert Zonis was posting regarding Leucidal before the site crashed. Through him and several other sources I heard rumblings regarding issues with Leucidal in the last quarter of 2013. Primarily the issues were with Yeast/mold coverage so Potassium sorbate is the way to address that.

    Grapeseed Extract is an over hyped "preservative." I will not open that can of worms, but I would not recommend it to anyone. Microformulation Cosmetic Consulting provides Custom Formulations for both large Commercial accounts as well as smaller entrepreneurs. We can provide Naturally compliant Formulations under the NSF, NPA, Whole Foods and USDA Organic Certifications. BS.Pharm Albany College of Pharmacy, Union University.
  • BobzchemistBobzchemist Member, PCF student
    We are currently testing Leucidal. At this point, I can't give any credence at all to unfounded rumblings and/or rumors.

    All I'll say about GSE is that opinions differ.

    I will also point out that we've found it to be extremely helpful to use a chelating agent whenever we use a "natural" preservative system.
    Robert Zonis, Sr. Formulation Chemist, Beaumont Products "All opinions and comments expressed are my own, have no relation to Beaumont Products, are fully copyrighted, and may not be used without written permission."
  • MakingSkincareMakingSkincare Member, Professional formulator
    edited January 2014
    Ben, thanks so much for your response.

    Re leucidal, that was my conclusion too - in the absence of independent studies confirming that it's broad spectrum, I don't recommended it on my preservative review page.  Ditto with the GSE.  Bobzchemist - would be great to see what your testing reveals.

    Great point about adding a chelator Bobzchemist.  Reducing the amount of "bug food", unbound water and adding auxiliary ingredients such as glycols also helps.
    Jane Barber (free online course)
    Formulation discussion forum (18,000 members):
  • tell me the tests done of a finished product in the micro lab
  • MicroformulationMicroformulation Member, Professional Chemist
    Chelating agents are able to enhance
    the efficacy of most preservatives. This occurs as the chelator removes
    metal ions from cell walls of the microbes. The weakened walls then
    allow the biocide to penetrate and destroy the microorganisms. Although
    the boosting effect of chelating agents on preservatives is well known,
    the environmental fate of these materials has been debated. To avoid the
    environmental discussion about chelating agents, readily biodegradable
    alternatives have been introduced to the market.

    I use a chelator with PE9010 each time to boost its efficacy. This need was passed onto me several years ago by Wolfgang Siegert at Schulke. It can be challenging as EDTA is a big no no in most "Natural" standards (NPA, NSG, WF's). In that case I will generally use Dermofeel PA-3 from Dr. Straetmans (Kinetik in the US). Microformulation Cosmetic Consulting provides Custom Formulations for both large Commercial accounts as well as smaller entrepreneurs. We can provide Naturally compliant Formulations under the NSF, NPA, Whole Foods and USDA Organic Certifications. BS.Pharm Albany College of Pharmacy, Union University.
  • Chemist77Chemist77 Member, PCF student
    @Mark In our old threads I read somewhere that apart from the 'natural standards' issue there was this efficacy issue as well. IIRC (learnt it from Duncan to concise everything) tetrasodium salt has to be used above pH 7 and disodium salt below pH 7. Could you please correct me if i am wrong??? Secondly, are there similar issue with sodium phytate too?????
  • Isaiah

    The only micro tests typically done on finished product are aerobic plate counts for bacteria and fungi.  Those tests tell a person how many bacteria and how many fungi are present in a given gram or milliliter of product, which in turn indicates whether or not the finished product meets a company's specifications for acceptable quality for release/sale.  Less than 100 bacteria or fungi per gram or milliliter is a common specification, though less than 10 bacteria or fungi per milliliter or gram is more typical for eye-area cosmetics.

    For testing help visit us at Cosmetic Test Labs
  • Thanks for the insight and information, Ben! I have already had great interaction with your lab. Andrew has been great to work with and also gave me great advice. And thanks for everyone's feedback on GSE. I appreciate the help. :-)
  • PolymergirlPolymergirl Member, PCF student
    Can you comment on the advisability of many "crunchy" homemakers who make their own liquid soap using regular soap (which they carve into flakes) and water?  It seems to me to be a potentially microbial mess, since they do not add preservative to the mixture.  Do you have anything specific I could tell them to warn them away from this practice? (I offered caution and recommended refrigeration of the product and to discard after one week).
  • BobzchemistBobzchemist Member, PCF student
    Getting the pH up to 12 would make those liquid soaps pretty much self-preserving.
    Robert Zonis, Sr. Formulation Chemist, Beaumont Products "All opinions and comments expressed are my own, have no relation to Beaumont Products, are fully copyrighted, and may not be used without written permission."
  • Polymergirl,

    I haven't heard of that practice before...probably means I spend too much time in the lab :)

    Anyhow, I am sure it's fine for the day or two.  Then after that I'm pretty sure it would turn into germ soup unless as Bob says the pH is very high. 

    For testing help visit us at Cosmetic Test Labs
  • MakingSkincareMakingSkincare Member, Professional formulator
    edited February 2014
    Ben - "germ soup" - love the phrase!    

    Polymergirl - there are a confusing number of preservatives available - you might find it helpful to look at this review of 27 of them  which details what the preservatives protect against, pH restrictions, compatibilities, %, what phase to add etc.  

    If you need any more help, feel free to PM me.
    Jane Barber (free online course)
    Formulation discussion forum (18,000 members):
  • PolymergirlPolymergirl Member, PCF student
    Yes, germ soup, that sounds like what they are making. 
  • @The_Microbiologist
    We have just a small skin care company and started to formulate natural skin care products. At the moment, we have formulated a moisturizing cream using natural ingredients such as coconut oil, avocado oil, cucumber extracts, vitamin E, etc. We used natural preservatives Parfum (Naticide) 0.8% and Potassium Sorbate 0.7%. Formulation is very good and cream is also very good. We sent for the Preservative Efficacy test and got the following result.

  • labtechnicianlabtechnician Member
    edited February 2014

    Time Point      S.aureurs            P.aeruginosa         C.albicans      A.brasiliensis

                            CFU/g               CFU/g                    CFU/g                CFU/g

    Inoculum         7.0 x 105              6.7 x 105                  6.9 x 105                1.7 x 105

    0 hour             6.8 x 105             6.1 x 105                  6.1 x 105                1.9 x 105

    7 days                < 10                   < 10                        [NA]                      [NA]

    14 days                 < 10                   < 10                    1.0 x 105                   150

    28 days                 < 10                   < 10                        < 10                       < 10                                   


    What is your opinion regarding this result? How I could reduce the
    survival of yest (C.albicans)? Your help will be really appreciated.


  • Hello labtechnician,

    I notice the "n/a" for Candida and Aspergillus at day 7.  I presume those organisms were just not analyzed at that timepoint.  Is that correct?  Was this by chance an ISO method? 

    Nevertheless this appears to be a well-preserved formula in general.  I see the same "odd" data that you do with regard to Candida.  It's strange for that organism to have what we would call a "shoulder" die-off curve, meaning slight reduction followed by precipitous reduction.  Usually Candida reduction is much more linear, meaning you'll loose a log (90%) or so each week on the way down to a final result of non-detection.  It's possible that the 14 day data was artificially increased by chance, by clumps of organism within the test material or something else.

    If USP <51> criteria were applied it would "pass" so you are in good shape.  If you want to be extra diligent, you could re-test just the Candida and see if next time you see a more linear (sort of more predictable and thus more dependable) die-off.  If you wanted to be even more diligent, you could do that at a different lab.  If two labs get the same result, it's almost certainly "real."

    Here is my last note, please verify with your lab that they did separate controls to verify neutralization and recovery from the test sample.  Ask them for the data for that, too.  They should have it and it should be quantitative.  If they don't, then they're not doing the test right and it calls into question much of the data.  Feel free to email me privately if that comes up and I'll help you work through it and re-interpret the data.

    For testing help visit us at Cosmetic Test Labs
  • What is naticide composed of? The INCI just says: Fragrance or Parfum.
  • labtechnicianlabtechnician Member
    edited February 2014
    @The_Microbiologist Thanks a lot for your kind help. yes this preservative efficacy test was performed according to British Pharmacopoeia (5.1.3)  method. I have asked lab for data regarding separate controls and will email you asap. thanks once again.

    @mikebavington.. Naticide is a blend of natural extracts formulated by SINGERA research. company says it is a fragrance that inhibits bacterial growth in cosmetic formulations. it is a good natural preservative

  • Hi Ben,

    I have a question.  I have been making lotion for my family to use.  I am currently preserving it with 2% leucicidal SF liquid and it seems to last 4 months.  Do you have any experience with adding aspen bark for additional preservative coverage?  I was reading about combining each at 2%.

  • Hi Compounder,

    I don't have much experience with aspen bark, sorry.  I don't know how you are determining the 4 month shelf life but if it's based on aesthetics the lotion is probably microbially contaminated long before you can perceive it visually. 

    As a point of reference, one can put 100,000 bacteria into a milliliter of water and the water will appear to the naked eye to be crystal clear and usually won't smell bad, either.  That all changes once you get to about 10,000,000 per milliliter.  Most of the cosmetics we test in our lab that have counts ranging into the tens of thousands or millions of cells per milliliter have subtle or no aesthetic differences from sterile samples.

    You may be determining shelf life with lab tests - I am just sharing for the benefit of the forum in general.

    Hopefully someone with experience with aspen bark can chime in too.
    For testing help visit us at Cosmetic Test Labs
  • Hi Ben, @The_Microbiologist

    I'm a fairly new microbiologist in cosmetics and have many questions that range from basic to philosophical in microbiology since I have started. I could talk about microbiology all day and the exciting bacterial growths I have come across but before I go on a tangent I have some quick questions of concern.

    First, I have had some growth of bacteria and it appears 100% of the time. I mean that i test the product 5 out of 5 times or sometimes 10 out of 10 and I get growth for this particular product "A". Also I have lets say product "B" which I have also had the same occurrence. When I send it out to 3rd party labs they say its clean. <10cfu/g. There was one instance they found more than 1,000 cfu in product A but the 2nd time around they found nothing.
    - Test are in USP methods and I use BD Letheen broth that has Licithin and Polysorbate 80 to neutralize preservatives so it says. From what i heard 3rd party labs are asked to do USP methods as well and probably use phosphate buffer as their broth. 

    Would this be a problem?  I have to probably reread USP <61> and see if neutralizing preservatives is just recommended and not mandatory. 

    Another idea i have is probably sample size used in testing. I use 10g to 90mL. 

    I have many more questions but i have run out of time for now. I hope you can help me and share your experience so I can be enlightened. I'll greatly appreciate it. 
    Thank you,


  • Welcome to the forum!

    Are the colonies that always appear on your plates the same type type, or do they vary?  Do they "run with the dilutions" meaning that there are more contaminants in plates that got more neutralized product and fewer in plates that got less?  If you haven't done a dilution series it's easy, just put 1/10 of what you would normally put onto a plate onto an agar plate and incubate, then compare with the ordinary plate. 

    If the contaminants "run with dilution" that's a good indication they're actually in the product (though it may also indicate they're in your neutralization medium) and you're just detecting them where other labs are missing them.  There are all sorts of ways labs miss neutralization of preservatives, too high of incubation temps, not long enough duration of incubation, etc.

    If the colonies appear on every plate regardless of dilution and especially if they're morphologically varied, then you probably have some sort of lab contamination going on and the product is in fact clean.  The contamination could be from air, technique in need of improvement, or even non-sterile plasticware marketed as sterile.  It happens.  Part of the art of microbiology is reducing the frequency with which such contaminants pop up and learning to tell environmental contaminants from product contaminants.
    For testing help visit us at Cosmetic Test Labs
  • Unknown Member
    edited June 2014

    Thanks for the greetings and reply. 

    I would assume they are the same but i might have to send it out to get ID. Its a gram positive rod and this product A is a powdery/grainy like dry product. I have diluted the sample 1/10 and 1/100 dilution and then spread a 1mL on to a TSA plate. 
    The 1/10 and 1/100 TSA plates looked the similar with confluent growth. I'll take pictures when I can. 
    My results:
    TSA: TNTC and Gram stain it (link has pictures of all plates and gram stain)

    MSA plate: 2 plates (from TSA) and there was yellow colonies one plate. 2nd plate yellow colonies but my streak looked like mucous and the colonies were gelatinous goo. 

    It is a great mystery that 3 other labs were unable to find growth. I do about 60 different samples a day and when product A shows up I come across the confluent growth again. I'm sort of out of ideas how to explain this. I did an side experiment with just using 90mL of sterile water and performed a 1/10 dilution. I still got growth on my TSA plate. HA. 

    I do all my work under Biosafety cabinet class 2 A2 and have positive and negative controls during my testing. It can be from environment since opening the drum causes white powdery mist that can be felt when breathing. Maybe some spores? 

    Thanks again.


  • Wow, the pictures really help!  What you are considering to be "confluent growth" I think is probably more along the lines of a "spreader," meaning a single or a few colonies that rapidly take over the plate either by rapid multiplication (which gram+ rods are great at) or other means.  The way you can check this is to look at the plate after just 12 or 18 hours incubation, then again at the end of the incubation period.  My guess is that you will have one or a few colonies only to begin with, then a couple of days later I imagine those colonies will have spread over the entire plate.  Do note the zones that on the plates in question that do not show growth.  If the product was very contaminated and the spread plating covered that part of the plate, I would expect growth there.

    The other explanation is that the plates are too wet, so you have a situation where microorganisms grow in the fluid on the surface (as if growing in broth) and then that fluid gets spread around the plate during movement and seeds other parts of the plate.

    There is no need to send anything out to get it ID'd at this point.  For practical purposes if you can't tell them apart on the basis of colony morphology, you can consider them the same organism.
    For testing help visit us at Cosmetic Test Labs
  • Unknown Member
    edited June 2014
    Yeah about the spreading... that might fall on my part since I am rushed to do some of the testing. X_X. I'll see about retesting it and doing a better job at spreading it. Then i'll check on it within time intervals. I was also going to try the pour plate method and see if that stops it from spreading.
     "Confluent growth" is the term that was coined for growth that spreads over the plate. I am new to this spreader type of bacteria definition. I know of Proteus likes to swarm over the plate so would that also be considered a spreader? 
    It's good to know that gram + rods are great at being spreaders. thank you. 

    If it is just a few colonies causing this spreading action would it be safe to assume my 1/100 dilution results be greater than 100cfu/g ? 

    I was curious about my MSA results that it managed to have yellow colonies and ferment the mannitol. I am beginning to see a trend that selective plate results have interesting results. I had EMB agar once with a contamination of Burkholderia cepacia and it had the metallic green sheen appearance similar appearance of E. coli  but I went back and forth plating with centrimide agar and EMB agar to confirm it wasn't.  .I couldn't find anything about B. cepacia fermenting lactose on EMB. Sometimes i get jungle of multiple organisms on plate. 

    If possible one more quick questions. In testing cosmetics would the type of neutralizing broth (D/E or LB) matter for testing yeast and mold? or would extra things need to be added to the broth? I assume that as long as its plated on a SDA plate it would be fine to grow any possible yeast or mold. 

    Thank you Ben, I greatly appreciate you helping me! :)

  • EliEli Member, PCF student
    Hello Ben, I have maybe two very stupid questions but ... Do saturation of germs can cause lost of transmittance in a water based solution?

    And another one ... If I dry a slurry full of germs (or leave a small amount of water) and leave it like that for several months... Adding water do they "wake up" again?
  • Hi ben

    whats different between parabens and isoiazlinon preservatives? are they longevity different?

  • Hi Eli,

    Yes, microbes will definitely cause loss of optical transmittance in a water based solution.  In fact, we use spectrophotometers to quickly estimate microbial concentrations in broth cultures.  Each little cell is sort of like a glass sphere when it comes to light, they cause the light to refract and go in all different directions, which means it doesn't wind up at the sensor (that is, it's not "transmitted")

    To answer your second question, I would have to know which microbes you're using and specifically what you're doing (what temperature, humidity, vessel type, etc).
    For testing help visit us at Cosmetic Test Labs
  • ZoeZoe Member
    Hi Ben 
    I am looking for some advice about effective preservatives to use with face masks containing Clay and in facial exfoliators when using exfoliating grains (such as bamboo) in a cream (water& oil) based formula. In the past I have used Phenoxyethanol and Ethylhexyglycerine, but I have since found out that these aren't effective enough against the Gram+ bacteria when going though microbial testing. Is there something I could add to assist this preservative? Ideally I would like to go down the natural route and have looked at using Dermosoft 1388 eco along with GMCY, do you think this would be effective? But equally I am not opposed to using other preservatives. I have a small scale uk based skincare company but not from a scientific background, so learning all the time! I would love to hear your thoughts…..many thanks Zoe
  • MakingSkincareMakingSkincare Member, Professional formulator
    edited June 2014
    Zoe, no-one can tell you whether a preservative will be effective or not.  You will need a lab test for that.

    What I can say is that the preservatives you mention (Phenoxyethanol and Ethylhexyglycerin and Dermosoft 1388 eco/GMCY), being the more "natural" type preservatives, will prove a real challenge to preserve the clay/bamboo.  Even if the clay has been irridiated, clays are problematic because they adsorb spores onto them and the large surface area makes it difficult for your preservative to cover everything.  Clays also tend to deactivate formaldehyde donor preservatives.

    Do bear in mind that there's a lot more to preservation than just adding a preservative eg reducing water activity, using packaging which minimises contamination in use, microbiological testing of raw ingredients and process water, etc and adding 0.1% disodium EDTA (heated water phase) and glycols will help. Another major factor is the amount of "bug food" in the formula - this often gives overlooked.  I see many people putting tea, goat's milk, honey, hydrosols, floral waters, aloe vera, extracts, protein, powders, starches etc in their formulas which will really challenge the preservative system - reduce these to a tiny % (eg 0.1%).

    More info including reviews of 27 preservatives -
    Jane Barber (free online course)
    Formulation discussion forum (18,000 members):
  • EliEli Member, PCF student
    Hello Ben,

    Thank you so much for your answer. That solved a big problem I had. Relative to the type of microbe or details of production sadly I do not have access to that information :( but it is nice to know that there might be some type of microbe that can "come back to life" somehow... Thanks again. !
  • Hi Eli,

    Microbes are notorious for propagating from seemingly out of nowhere...when you have liquid around nutrients, you can count on them showing up at the party. 

    In fact, they pop up so quickly and reliably that people literally used to think that they spontaneously generated (appeared from nothing).

    I'm glad my comment was helpful.


    For testing help visit us at Cosmetic Test Labs
  • edited July 2014

    I have been using the leucidal liquid and Phytocide Elderberry Extract at 2% and 0.5% respectively for my oil in water emulsions. This combo has been very effective though I am in a quandary for 2 reasons: 1. Needing to use this high amount means that the preservative costs is quite high, especially in relation to the rest of the formula. 2. Is it better to use a 'natural' preservative at this higher % or a synthetic preservative at a much smaller %?

    I want to keep my customer base that want paraben free and I am looking at my options to reduce the costs and preservative. I would be happy for any information and feedback. I am wondering if I can use these at a lower rate with other combinations - potassium sorbate? phenoxyethanol?

    I have just purchased Geogard Ultra to experiment with and am finding that it too needs at least 1.5% and am seeking information if I should combine it with something else.

    I have tried Opiphen plus, but I wasn't happy with the end result.

    Thank you,
    Regards, Kathy
  • MicroformulationMicroformulation Member, Professional Chemist
    edited July 2014
    Dear Kathy,

          First and foremost I cringe whenever someone throws out "natural" vaguely. It isn't a defined term at heart and it needs to be qualified. If you are trying to meet your clients demand for "safer" products. I would investigate the Natural Standards (NSF, NPA, USDA), learn one, endorse it and then use it as a qualifier for your ingredients. This is simpler, it gives you third party validation and you can move onto what is more important, the performance of your product. If you leave it undefined you will either be too non-compliant (green washing) or too scared to use anything. Using the Internet/Google as your ingredient validation is dangerous. Nobody will agree and you can argue all day long. You can make most Cosmetic Chemists grumble by even mentioning the "paraben scare" and you can infuriate the super strict "natural good, synthetic bad" crowd by telling them about naturally occurring parabens. Endorse a standard and get out of the whole muck pile.

         There are numerous preservative systems with long records of success and lower costs available and endorsed under the Natural standards. Their inclusion is generally not controversial and both camps (strict, mainstream industry) can generally agree.

          That said, can I recommend any ONE preservative that you can buy, use in every product and buy exclusively? ABSOLUTELY NOT!!! When selecting a preservative the entire Formulation must be taken into account. If it is a surfactant system, will a preservative for a basic cream work? Not necessarily. I encourage you to take a look at the FormulaProtect site that Lonza has and run a Formula through their decision engine. In the end it spits out a Lonza preservative of course, but you will be able to see how many factors will come together to suggest a best preservative on a case by case basis.

           Other factors contribute to the preservation strategy as well. Some packaging is more secure than others. For example a lotion pump would provide more protection than a jar. Final pH of the product has an effect. For the informed Formulator adding a glycol can augment the preservative system.

            Sorry I didn't answer your question outright, but I think my point is that preservation takes some due diligence and research. Jane at Making Skincare (she can chime in) has some documents that will give you an overview of preservation. Again, it is not impossible to learn preservation but it does require more information than could be included efficiently in a single or even multiple discussions. I read 4 Journals a month plus multiple RSS Feeds and Professional blogs. I would estimate that at least 30% of that reading is in the area of preservation and new preservatives.

             Lots of information. I hope I didn't discourage you or come off as pedantic. It is simply a topic that needs more than time and effort than a blog can deliver. As for wanting just ONE preservative for everything the best analogy I can give you is in food. I am letting you buy ONE condiment for every meal you cook. To paraphrase some arguments I have heard in preservation "I only want to pay for 1 condiment, paprika is too expensive, etc." You can have salt, but not pepper also, You might want Paprika but you can't get it retail. Any good chef would balk at that scenario. You can't limit yourself to one preservative as well as a universal preservation panacea. It doesn't work. Microformulation Cosmetic Consulting provides Custom Formulations for both large Commercial accounts as well as smaller entrepreneurs. We can provide Naturally compliant Formulations under the NSF, NPA, Whole Foods and USDA Organic Certifications. BS.Pharm Albany College of Pharmacy, Union University.
  • EliEli Member, PCF student
    Hello everybody! I was wondering some things about microbiology because i went to a cosmetic event yesterday where one of the speakers said: Maybe in the future cosmetics will be treated as food, and they will be store in the fridge ! and that phrase keeps moving in my mind .. Is it really possible? maybe it is actually a good idea but too expensive to create the chain of cold.. from supermarkets and distributors etc.. 

    My question is, does every cosmetic form need a preservative system ? like powders (dry shampoo), or oils (i guess oils can also develop microbes). Would it be useful to use the fridge once we open a cosmetic product and start to use it ?

  • BobzchemistBobzchemist Member, PCF student
    Anything that is used on skin needs a preservative system, just to be safe. The stupidity of consumers should never be underestimated (spit in mascara? Really?).

    I would say that the only way to make a completely safe cosmetic without preservation would be to make it sterile, and then package it aseptically in refrigerated single-use containers - but guaranteed, someone would try to stretch it out, and put a half-empty open container back into the refrigerator.

    The difference between food and cosmetics is that the human digestive system is designed to cope with a wide variety of micro-organisms, so food can be a bit contaminated, and still safe to eat - but the human eye is not designed that way, and a little contamination can be disastrous.

    Then, we must also consider legal liability and consumer lawsuits - if a consumer claims injury from a product, and it tests positive for bacteria? The company that made it, and everyone who had a hand in formulation and QC, may be in big trouble.
    Robert Zonis, Sr. Formulation Chemist, Beaumont Products "All opinions and comments expressed are my own, have no relation to Beaumont Products, are fully copyrighted, and may not be used without written permission."
  • EliEli Member, PCF student
    Thank you very much for the answer Bobzchemist, pointing out the exact difference btw food and cosmetics made me realize it is a serious thing when we talk about safety in cosmetics.. you are right ! The eye doesn't have defense systems like the digestive track.. great example!

    About lawsuits it is still a mystery how a consumer can prove the bacteria comes from the use of that specific cosmetic? If consumer is always right, then big companies must be scare about them. .. 
  • Hello everyone! I am new in microbiology and have a lot of question to ask, especially in PET test.

    1. How to do a micro challenge test for the W/O cosmetics? I have read the summary of CTFA-6(through this link, but it just mentioned one method as that:"reduced the inoculum volume or oil based carrier system", I want to know how to reduced the inoculum(centrifuge?)? And oil based carrier means I need to put the microorgnisim into oil? What kind of oil? 

    2. CTFA-6 also mentioned molds surface inoculation for W/O soild products, I want to konw how to inoculate and how do the judge? I think spray or inoculate with a disc of media may be practical method, but I do not know if it is right?

    3. Do you have good research artical or report to reconmend?

    Thank you so much!

  • Really really fantastic thread!
    Rich information from all the experts.
    Thank y'all.
  • PerryPerry Administrator, Professional Chemist
    This really was an excellent thread.  I'll have to seek other experts to do a Q&A
  • martmart Member
    edited September 2015
    I have a question for the microbiologist. I am working with a product that has benzyl alcohol at 0.08% . Is this enough to preserve it? The PH is 4 and it is about 50%.water I am debating on adding something extra but dont want to if not needed. Maybe PG ? What would you recommend ? Parabens are unacceptable. I can drop the PH , slightly. Thank You.
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