Preservative for pH 9-10 liquid soap

What are my options for an alkaline based hand soap solution preservative?
Does a liquid hand Castille soap mixed with oils and glycerin need a preservative? 
Many thanks in advance for any help/advice given!

Comments

  • @Leo Usually bar soaps from saponification of either tallow or vegetable oils, are the ones that are basic (alkaline). If you have a liquid soap, you could actually have it at a pH closer to the skin (roughly around 4.5-5.5). If you want to stay at that pH range, isothiazolinones are very effective, same as formaldehyde-releasers (like DMDM hydantoin, Diazolidinyl urea, etc.), but that is if you're ok with that type of preservatives. 

    I do believe your liquid Castille soap needs since you need quite some watter to haved in a liquid form. 
  • LeoLeo Member
    Will the acidification with for instance citric acid as a preservative affect the foam?
    Are there any other preservatives that are "more natural" that can function at pH 9?
  • If you lower the pH you will loose the bubbles. 
  • Here is an ingredient list. No preservative but an antioxidant. Look at the advisory information.😱

    INGREDIENTS (INCI): Aqua, Potassium Cocoate (Saponified Coconut Oil*‡), Potassium Palm Kernelate (Saponified Palm Kernel Oil*‡), Potassium Olivate (Saponified Olive Oil*‡), Glycerin*, Potassium Hempseedate (Saponified Hemp Oil*), Simmondsia Chinensis (Jojoba seed oil*), Citric Acid, Tocopherol (Vitamin E), Helianthus Annuus Seed Oil (Sunflower Oil) *Certified Organic Ingredients/ ‡Certified Fair Trade Ingredients

    Advisory information:

    Vegetarians and Vegans. Don’t drink soap. If cap clogs, poke it clear, do not squeeze the bottle. Soap can clog and spurt with pump dispensers. Keep out of eyes. Flush eyes well with water for 15 minutes. Consult a physician if irritation persists.

  • If the liquid soap has a pH 9 - 10, a preservative is unnecessary. Refer to ISO
    29621 "Cosmetics — Microbiology — Guidelines for the risk assessment and identification of microbiologically low-risk products."

    We have a GMP Certified production facility producing a lot of liquid soap, and export globally. These products are Notified with cosmetics authorities and all the necessary testing is done in our in-house labs and verified by external labs.


    Dr. Mike Thair
    Cofounder & Chief Formulator
    Indochine Natural
  • ketchitoketchito Member
    edited September 12
    @Leo  If you have a liquid soap, you'd need to go very low on pH to prevent microbial growth, and as @Dr_Sara mentioned, it'll impair foam and detergency, and it'd also increase the chance of instability (for instance, CAPB behaves as a cationic at low pH, which will interact with anionic surfactants forming a precipitate). It can be done, but you should be very careful with the ingredient selection...also, you'll need a very good GMP system in place to guatantee that your water for instance is of very high quality, since low pH helps prevent microbial growth, but it won't avoid your product being contamined from external sources.
  • LeoLeo Member
    If the pH of the soap is around 9, do I need a preservative?
    I see that a lot of these products have citric acid which affects foaming and performance?
  • @Leo Citric acid in a liquid soap at a pH above 9 will be present as its salt (Citrate) rather than the acid form.

    Regarding the need for a preservative, if your idea is not to include one, there are a couple of readings you might want to take a look at: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1468-2494.2009.00492.x, https://makingskincare.com/preservatives/.

    So, pH as a sole strategy could be tricky, since being at least at a pH of 10 for shrinking the risk of microbial growth (I've seen products being contaminated at pH around 9), can also mean that you might have free alkalinity in your product. Of course this is more sensitive for leave on products, but for individuals with reactive skin (not to mention if the product reaches your eyes) and under repetitive use, that might cause some problems.  
  • for true soap- a pH of 9 is good. I would add a preservative. 


  • LeoLeo Member
    What preservative would work at pH near 9? 

    CAPRYLHYDROXAMIC ACID?

    propanediol?

    Please let me know.
  • LeoLeo Member
    glycerol monolaurate or monolaurin or propanediol or caprylhydroxamic acid to name a few. Any experience with these or other preservatives for pH near 9?
  • Hi @Leo I have used phenoxyethanol in liquid soap.
  • LeoLeo Member
    Does anyone have experience using Suttocide A (Sodium Hydroxymethylglycinate) as the preservative at high pH above 9-10?

    How about Euxyl K940 ( INCI name: Phenoxyethanol, Benzyl Alcohol, Ethylhexylglycerin, Tocopherol)
  • @Leo Suttocide A is a very powerful preservative (if you don't mind that it's a formaldehyde donor, of course), I believe you still need to add an antifungal. 

    But I believe Euxyl K940 might also lack of the same activity since Ethylhexylglycerin is not a powerful antifungal.  
  • LeoLeo Member
    What antifungals do you recommend and at what concentrations?
  • @Leo Organic acids like Benzoic or Sorbic acid work well for this purpose (you can get them as their salts: Sodium benzoate or Potassium sorbate). You can start at 0.3%. 

    But if you don't mind using a formaldehyde donor, then Glydant Plus or Liquid Germal Plus are very good broad spectrum preservatives. You can find a lot of literature about them. 
  • PhilGeisPhilGeis Member, Professional formulator
    ketchito said:
    @Leo Organic acids like Benzoic or Sorbic acid work well for this purpose (you can get them as their salts: Sodium benzoate or Potassium sorbate). You can start at 0.3%. 

    But if you don't mind using a formaldehyde donor, then Glydant Plus or Liquid Germal Plus are very good broad spectrum preservatives. You can find a lot of literature about them. 
    Organic acids would be useless in alkaline products, including liquid soap.


  • PhilGeisPhilGeis Member, Professional formulator
    edited November 24
    mikethair said:
    If the liquid soap has a pH 9 - 10, a preservative is unnecessary. Refer to ISO
    29621 "Cosmetics — Microbiology — Guidelines for the risk assessment and identification of microbiologically low-risk products."

    We have a GMP Certified production facility producing a lot of liquid soap, and export globally. These products are Notified with cosmetics authorities and all the necessary testing is done in our in-house labs and verified by external labs.


    Liquid soaps can be contaminated.   I've observed actual colonies of bacteria in/on amended bar soaps.  
    ISO 29621 claims pH >10 as cutoff for preservation, not 9-10.  Recall please ISO's are concensus decisions - good as a guideline but not absolute.  Certainly one can have microbial contamination at >10.  

    Please also recall that preservation is primary intended to protect the product in-use, not as delivered.  In this, packaging is an important preservative element - maybe the most important for some products.

    Have you in-use data for your application?
  • LeoLeo Member
    @PhilGeis Sir-the packaging for the liquid soap (pH 10) is a plastic container with a foam pump.

    Is a micro challenge recommended and definitive?

    Which preservative(s) would you use?

    In your experience, regarding a different product, have you heard of microbes contaminating a gel at pH 11?
  • PhilGeisPhilGeis Member, Professional formulator
    Leo said:
    @PhilGeis Sir-the packaging for the liquid soap (pH 10) is a plastic container with a foam pump.

    Is a micro challenge recommended and definitive?

    Which preservative(s) would you use?

    In your experience, regarding a different product, have you heard of microbes contaminating a gel at pH 11?
    Not sure I'd preserve that soap.  Is this a cosmetic?  How effective do you see the package as protection?  Perhaps do some in-use exppsure.

    ph !1 gel.  Can you tell me smething about the product?  At that pH - is it a cleanng product?


  • PhilGeisPhilGeis Member, Professional formulator
    edited November 25
    Let me also add -  as the pH becomes extreme, the classic PET becomes less useful - the product "passes" with or without preservaton even tho suscpetible to contamination.  Be aware -the USP bugs are lab creatures that happily grow at ~ neutral pH where they'd lived since initial submission to ATCC up to 80+ years from isolation - on neutral pH media.
    Also - the product contaminants as pH's become extreme start to engage with extremophiles that won't grow well (potentially won't grow at all) on conventional media but will still deteriorate the product.  Those bugs contaminating at extreme pH are less likely to be pathogenic but preservation at those pH's is a real pain.
  • LeoLeo Member
    @PhilGeis What plastic or other packaging materials hold up at pH 10-12 over time?

    The product at pH 10 is a liquid soap and the product at pH 11 is an anti-wrinkle gel.
  • PhilGeisPhilGeis Member, Professional formulator
    edited November 25
    I'm sure no packaging expert - but Clorox bleach (e.g. pH 12) -  think it's in HDPE.  http://menda.descoindustries.com/PDF/ChemicalResistanceChart.pdf
    Are you sure the anti-wrinkle is safe - esp. if used near eyes?
  • LeoLeo Member
    Chlorox bleach is neutralized to a much lower pH than 12.
    Household Bleach is usually at pH 11-13 depending on use.

    Common soaps have a pH of between 9-11 and have routine warnings to keep out of eyes and what to do if soap gets in your eyes. 

    The pH 11 gel will be used near the eye but it rapidly dries upon skin contact (within one minute). It may, in some, produce an intended mild irritation and mild redness of the skin that resolves after a few minutes. Once dried upon contact with skin, it cannot harm the eye.

    Soap will do more harm to the eye since it is lathered and foamy and people tend to spread soap into their eyes during application. The key is to NOT get the gel in the eye during application with your fingers (which you have much more control than with soap).

    Instructions: Apply to crows feet and under the eyes. Keep out of eyes. Do not apply to eyelids. Keep each eye closed until product is fully dried! Do not apply with other products.

    Additional instructions will be provided if the gel gets in the eyes (rinse immediately with water and seek medical attention if eye irritation develops, etc.). Instructions will also be provided to address if irritation of skin is severe or persists.

    One has to take risks if one wants to use a product that performs and provides effects on eye wrinkles!

    If the product does not produce some form of harmful effect, it will not affect wrinkles....and will only be another marketing BS story....

    The goal is to help 99% and expect that there will be a vocal 1% that will complain.
    The media focus will always be on the vocal 1% and is the reason our society is becoming non-functional...like cosmetics in general.
    Covid as a prime example! We are planning to vaccinate our entire population to preserve the 1% that are expected to die....



  • @Leo Clorox bleach uses Sodium hydroxide in its formula to stabilize hypochlorite ion, which is a powerful yet unstable oxidizer. The pH that @PhilGeis mentioned for Clorox bleach falls correctly within the pH range for this product.  

    I honestly wouldn't apply such a high pH gel near the eyes. We need to consider that consumers commonly missuse products. And even if they use it correctly, that area of the skin is very thin and with less production of sebum, which not only doesn't help skin buffer the pH change induced by the product, it also makes skin more prone to irritation. Alkaline soaps wil do more harm not only because of the pH, but because of the type of surfactants present in the formula, which are capable of denature proteins and induce an immune response. 

    There are many ingredients that can be more safely used to fight wrinkles in that area (there are few of them with proved efficacy), so it'd be an option to explore some of them. 

    Your example for Covid is missleading, but I believe is not worth discussing in this platform.
  • PhilGeisPhilGeis Member, Professional formulator
    edited November 27
    Leo said:
    Chlorox bleach is neutralized to a much lower pH than 12.
    Household Bleach is usually at pH 11-13 depending on use.

    Common soaps have a pH of between 9-11 and have routine warnings to keep out of eyes and what to do if soap gets in your eyes. 

    The pH 11 gel will be used near the eye but it rapidly dries upon skin contact (within one minute). It may, in some, produce an intended mild irritation and mild redness of the skin that resolves after a few minutes. Once dried upon contact with skin, it cannot harm the eye.

    Soap will do more harm to the eye since it is lathered and foamy and people tend to spread soap into their eyes during application. The key is to NOT get the gel in the eye during application with your fingers (which you have much more control than with soap).

    Instructions: Apply to crows feet and under the eyes. Keep out of eyes. Do not apply to eyelids. Keep each eye closed until product is fully dried! Do not apply with other products.

    Additional instructions will be provided if the gel gets in the eyes (rinse immediately with water and seek medical attention if eye irritation develops, etc.). Instructions will also be provided to address if irritation of skin is severe or persists.

    One has to take risks if one wants to use a product that performs and provides effects on eye wrinkles!

    If the product does not produce some form of harmful effect, it will not affect wrinkles....and will only be another marketing BS story....

    The goal is to help 99% and expect that there will be a vocal 1% that will complain.
    The media focus will always be on the vocal 1% and is the reason our society is becoming non-functional...like cosmetics in general.
    Covid as a prime example! We are planning to vaccinate our entire population to preserve the 1% that are expected to die....



    Clorox bleach is 12 pH ("12.1" on MSDS/SDS - https://www.thecloroxcompany.com/wp-content/uploads/2020/03/Clorox-Regular-Bleach2-Bilingual.pdf) in the package, and please recall the observation  of Clorox pH was in ref. to your question re. packaging (bottle composition).  It is not neutralized for packaging and would be unstable if it were.  The only significant difference between Clorox and "common household bleach" is purity, not Na hypochlorite concentration or pH. 

    Common true soaps are rare and do not bear an eye warning - unless they make cosmetic claims, they're they're regulated only by EPA/CPSC not FDA.  In any case,  I don't understand their risk to eyes relevant to your pH 11+ product.   Covid comparison is profoundly irrelevant both in concept and in FDA/CPSC risk considerations and enforcement.

    To the point - what are your in-use data that defend the safety of the pH 11 product usage?  You should be concerned with any % that "complain" when that complaint addresses a safety issue.  Please recall - FDA policy addresses safety in use, not for 99% - but safe in use.  Safety is an affirmative data-based consideration - not the imagination of the seller.  If you're making cosmetic claims, suggest you consider labeling in compliance with 
    Cosmetics With Unsubstantiated Safety

    Warning--The safety of this product has not been determined.

    21 CFR 740.10



    Not sure if you're joking re. "One has to take risks if one wants to use a product that performs and provides effects on eye wrinkles!"   If not - would you mind sharing your name and product? 
  • LeoLeo Member
    @ Ketchito and @PhilGeis.

    There are NO cosmetic ingredients that have a functional effect on wrinkles for which a truthful anti-wrinkle claim can be made! Claims associated with cosmetic anti-wrinkle ingredients are marketing exaggerations/artful language with no proven functional effects in real life against wrinkles.

    To my knowledge, Retin A is the only ingredient with an FDA anti-wrinkle claim--please correct me if I am wrong. The professors in the 1980s in Dermatology were fantastic (Kligman and VanScott and others) and always made mention that without some level of irritation (peeling, redness, etc.), wrinkles will not functionally improve. The anti-wrinkle effects with Retin A are directly proportional to its ability to irritate skin over time. A reduction in the dosage or the formulation of the Retin A to make it less irritating (a cosmetic function), dramatically abolished its ability to visibly affect wrinkles.

    The best that we as cosmetic formulators can hope for with effective anti-wrinkle products is to temporarily mask the wrinkle in some unique way. The sodium silicate (liquid glass) ingredient in association with clay/mineral ingredients can perform this function and has an optimum effect in tightening/masking the wrinkle on skin at pH of 11 (personal observation). There are a number of products in the market with this ingredient at a pH of 9-11(Plexaderm, etc.). The skin can get temporarily red and mildly irritated in some patients (including myself) but the effects on hiding the wrinkles are fantastic. I have tested 100s of patients with a specific formulation containing the silicate --none had severe irritation of the skin that required acute or chronic care for a burn or ulceration of the skin. 

    The safety of this product has been determined--
    Do not apply the product to irritated skin.
    Do not apply with other products.
    The product may produce a mild irritation/redness of the skin and (like some soaps on the market) can cause eye irritation if it makes contact with the eyes. 


  • PhilGeisPhilGeis Member, Professional formulator
    edited November 29
    You have tested 100's  - so what has been the reaction of the "vocal 1%" who complained?   Was this you literally or in controlled clinical study?   As you know, it's important that subjective  observations with out easy metrics be conducted by uninterested experts.
     
    And what is the product, please?
  • LeoLeo Member
    @PhilGeis A few people had mild transient redness including myself. I am still searching for the 1st major complain (1% adverse event was an expected assumption).

    The product is in field testing by medical dermatologists and is expected to be marketed next year. No controlled clinical study is needed since the product has immediate effects that can be visualized by the user and the dermatologist.

    A controlled clinical study is not needed to determine if a forceful punch on the face will produce an immediate visible injury that is effective at reducing the wrinkles around the eyes (irritation and swelling)--this is a fun statement but also the truth--I can vouch for it as being a very effective anti-wrinkle method that lasts for days.

    The main active is the silicate ingredient in combination with another unique  ingredient that expands its activity 10x without adding harm.

    The most important factor is the immediate WOW sensorial effect vanishing the wrinkles within minutes. 

    No placebo/nocebo ingredients with elegant language promising hope in a bottle.



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