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% NaBenzoate, KSorbate? Anhydrous Formula
Hi there,
I’d like to use NaBenzoate, KSorbate, NaDehydroacetate, Na Phytate in my dry formula (like a shampoo bar). What are the percentages of each I should use?
I tried 0.3% NaBenzoate, 0.5%KaSorbate but it left a slight burning sensation/rash on my face. I’m guessing it’s the NaBenzoate and want to lower it, but was wondering whether dialing it down to 0.1% will even be effective against bacteria in my anhydrous formula.
NaBenzoate
KSorbate
NaDehydroacetate
Na PhytateThank you in advance.
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20 Replies
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Are you sure you need preservation?
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You probably don’t even need to preserve it but you could just use potassium sorbate to just prevent mold. I also don’t think sodium phytate is necessary in this case either because you aren’t having to protect the surfactant system when it’s in this format.
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thank you! but it’s left in a warm, moist shower after use..water will inevitably touch it. Bacteria will inevitably grow because I have xanthan gum in my formula. Could I use 0.05% of benzyl alcohol +DHA against bacteria?
I’ll def use Ksorbate against mold.
TIA
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Are you certain the sodium benzoate is causing the irritation? It is commonly used at this sort of concentration. As a shampoo bar is concentrated, could it be the act of rubbing the concentrated surfactants directly on the skin? Surfactants are irritant to the skin, but we don’t notice it as much when they’re at, say, 12-20% in a liquid formulation. A solid formulation is far more concentrated.
Sodium benzoate and potassium sorbate work by being pH adjusted to below 4.5 in the formulation, changing to benzoic acid and sorbic acid, which are effective preservatives. If the pH moves above this, the preservation system will no longer be effective. As you can’t control the pH of the water in your customer’s shower, I would suggest that these preservatives might not be as effective as you hoped. Perhaps you could trial including some crushed citric acid in the formula to pH adjust the water that does come into contact with your product? Honestly I’m just brainstorming here.
Interestingly, certainly on the UK market, there are a number of shampoo bars which are not preserved. The manufacturers claim that the nature of the product prevents bacterial growth. I found another containing benzyl alcohol.
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Still wonder if you need a preservative. You’ll never preserve water that might pool around the bar in a dish - but are you sure bugs will actuially grow on the bar?
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Besides, the salts won’t dissolve in an anhydrous formulation and because it’s usually the free acids which are antimicrobial, you can’t even obtain these by lowering the pH.Why do you have xanthan gum in an anhydrous formulation?If ever, use benzoic and sorbic acid, not their salts. Phytate… well… that one requires water to become active. If it’s added for increased lather (binding calcium from tap water), then you’d be better off using a different chelate.If you’re concerned with fungi, maybe add an undecylenic acid derivative. Perfectly fit into anhydrous products such as soaps and they won’t leach or behave hygroscopically. -
Soaps do not require preservation unless substantially ammended with compromising materials such as milk- and in my experience, that wsa bacterial contamination.
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High amount of surfactants also don’t need preservative.
What percentage of surfactants do you use in your Shampoo bar? -
The burning sensation is most likely from the Potassium Sorbate which you have at quite a high level … more around 0.15% would be appropriate. Potassium Sorbate often causes a flushing reaction in people who are sensitive to it.
But, without knowing what else is in your formula, it is not possible to really tell, but your high level of Potassium Sorbate sticks out.
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@MarkBroussard potassium sorbate was the culprit after all. some others didn’t report a reaction it tho…but it made me burn all over. Why are some like myself so sensitive to it? Is it a certain skin type? Does anyone know?
Thank you all!
btw there is pink bacteria growing on my bath tile..this is the thing im trying to preserve against as i read is airborne
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Anyone can be allergic to any chemical at any time … it’s all a matter of whether your immune system sensitizes you to any particular allergen
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Pink? Maybe Serratia marcescens - a potential contaminant but like not able to grow in concentrated surfactant. Could it be a yeast-like fungus - a Rhodotorula sp.?
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@PhilGeis. i think it’s Serratia marcescens. It’s all over the bath tile but not in the shampoo itself
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Aha!! Not on shampoo bar? Maybe a sign you don;t need preservation?
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Maybe it’s time you clean your bath? I mean, S. marcescens is a beautiful microbe but I wouldn’t want it all over my bathroom walls. It’s also an opportunistic pathogen which may cause pneumonia and the like and is quite hard to treat due to several inherent antibiotic resistances.
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Climatechangeanxiety said:@MarkBroussard potassium sorbate was the culprit after all. some others didn’t report a reaction it tho…but it made me burn all over. Why are some like myself so sensitive to it? Is it a certain skin type? Does anyone know?
Thank you all!
Those with rosacea and atopic dermatitis will have more reactions, but there are some people even without sensitive skin that will have side effects.Sorbic acid makes my face flush red like a tomato, (no reactions to potassium sorbate) but I don’t have what I consider sensitive skin. In fact, I can handle many “harsh” topical acne medications just fine.My local dermatologist explained to me that 1) anyone can have allergies and sensitivities at any time and 2) she thinks genetics and hormones/hormonal fluctuations are involved in some reactions, particularly in women.This paper here (full text) may interest you, as well as this one about sorbic acid (abstract). -
@RedCoast the refs are super helpful - thank you!
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@Pharma but I really love having pink bath tiles! Kidding, I am disinfecting away
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@PhilGeis is it bad that i have 33% guar gum in my dry / solid formula?
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I’m just a micro guy so hope others Perry, Microformulation) can address product formulation realities. Unless it brings a substantial bioburden or hygroscopicity elevates Aw too high, I’m ok.
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