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microbial challenge
I make a W/O/ foundation formula， and I use 0.35% Diazolidinyl Urea， 0.2% methylparaben，0.19% propylparaben， do someone know it can pass microbial challenge test？
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17 Replies
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The ONLY way to find out is to actually run the challenge test. It is impossible to even guess at results without the full formula.
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And even if we had the full formula, you still need to run the microbial challenge test to verify.
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@Perry,
Why do you think people assume that we have some sort of crystal ball that will automagically predict stability and/or micro results? -
Do you mean I need to stop using my Cosmetic grade Magic Eight Ball?
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Is that the one that says “Pass”, “Fail”, “Stable” and “Unstable”?
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Hi raywillping,
Unfortunately it’s true. Even with traditional preservative packages they have to be challenge tested. I have seen instances where formulations I expect to work fail the test, and vice versa.
Good luck!
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Another option would be to get a time machine, then go well into the future and see if the product is germy.
Unfortunately my time machine seems to be broken. I can only get it to go forward at normal speed.
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All kidding aside, there are a number of common ingredients, mostly surfactants, that act to inactivate preservatives. On top of that, the processing matters, as does which phase of the emulsion the preservatives end up in.
It’s not a simple question, unfortunately, and does not have a simple answer. If you are a professional, a number of the preservative suppliers will challenge test your product for free. -
Yes - if the preservative can withstand heat (even if it’s oil soluble), put it in the heated water phase of an emulsion to help guard against partitioning at the oil-water interface.
Some other tips (copied and pasted from http://makingskincare.com/preservatives/):-Add a chelator to help the preservative, lower the water activity, reduce any components that may be nutritive to the bacteria and fungi eg carbohydrates, proteins, organic acids, inorganic salts and vitamins.Mix up your preservatives, as they all have their strengths and weaknesses in what they kill, so a combo can give you a broad spectrum, and keep the overall levels of each down low, which helps with both stability and irritancy.Do put in place a strict GMP protocol to include microbiological testing of raw ingredients and process water, equipment sanitization.Design your packaging so it prevents contamination during use. -
you know， challenge test will cost much money and my boss do not want spending it for nothing （I means it maybe failure）。 and we have make a challenge test of mascara， and it is pass， we use 0.2% methylparaben 0.1% propylparaben and 0.35% Diazolidinyl Urea。 so I guess It will be OK。 but I am not sure。 is there anyone can show some Successful experience？
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No one can do that… As said above, there is a lot of parameters… If we could know without the challenge test, nobody will do that test anymore !
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In another post, @The_Microbiologist gave us an unofficial version of an in-lab indicator for challenge test success or failure. It still requires several plate counts, however.
Personally, I think that if your company cannot afford the cost of challenge tests, you should not be making any products that require them. Stick to anhydrous products, it’s less risky, both for your customers and your company. -
Do you need help explaining the concept of “some surfactants make preservatives stop working” to your boss?
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@Robert where can I find a concise summary or a reference where this inactivation of preservatives in presence of surfactants is mentioned??? I would very much like to stay abreast on this one as we all use surfactants and preservatives very often.
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@milliachemist, That’s a good question, and I don’t have one easily available.
@MakingSkincare or @The_Microbiologist, do you have anything like this? -
Yes, I found some articles eg http://www.cosmeticsandtoiletries.com/formulating/function/preservatives/85519567.html?page=2 and presentations which mention this. I then enquired further with some microbiologists here and in my group. One example - see third comment -I then updated my page reviewing preservatives and tips for formulating to reflect my findings - http://makingskincare.com/preservatives/
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@bobzchemist - Well, I think people are always looking for shortcuts and asking questions like these are the best way they know how.
But I agree, if the company cannot spend money to ensure that their products are safe they absolutely shouldn’t be selling them or in that business. I mean really, how much money are we talking about, a few hundred dollars? That should all be rolled into the cost of doing business.
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