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Co Surfactant
Hello,
What is the science behind co surfactants reducing the irritation of primary surfactants? I know it has something to do with water tension but not sure how having two surfactants makes a difference in irritation of skin? -
9 Replies
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To my knowledge (which is in this regard over 10 years old): Nobody knows (knew) why or how. It was all speculation to the point where I didn’t really bought into it. At least, it’s a mix of several different factors playing a role.Probably there’s new knowledge available… Hence, you pose a very good question here! -
I am having difficulty believing it myself. The only resource I have found is the following:
https://www.researchgate.net/figure/Structure-of-micro-emulsion-Microemulsions-were-not-really-recognized-until-the-work-of_fig2_236151177 -
The reason I am looking into this is that I am trying to formulate a shampoo that hopefully will not irritate my sons’ eczema.
So far this is my formulationAqua 74.5%
Sodium Cocoyl Apple Amino Acids 10%
Cocamidopropyl Betaine 8%
Hydroxypropyltrimonium Honey 3%
Aloe Barbadensis Juice 2%
Gluconolactone (and) Sodium Benzoate 1.5%
Guar Hydroxypropyltrimonium Chloride 1%I was taught in school that having the cosurfactant will make the primary surfactant less irritating. However, I wonder if just having Sodium Cocoyl Apple Amino Acids at 10 % would be mild enough without Cocamidropropl Betaine?
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I am not absolutely certain, bit I think It really all depends on what surfactants you are using to begin with. Say you are using Coco-Glucoside (non-ionic) as a primary surfactant … I find it highly unlikely that adding SLS (anionic) to the mix would make the Coco-Glucoside less irritating.
It could be simply a matter that adding a second surfactant that is less irritating than the primary surfactant helps because you simply have less of the irritating primary surfactant in your total surfactant load.
As an aside … you combine two surfactants together in a cleanser … how do the surfactants know which one is the primary surfactant which one is the secondary surfactant? … I say that because the whole concept is rather ridiculous to me.
Rather, focus on the type of surfactants you are combining together … Anionic surfactant irritancy may be reduced by combining with a non-ionic surfactant, for instance. Same concept as when you combine surfactants of different types (anionic + amphoteric, etc.) to build viscosity.
If your son has Eczema, I’d take a good look at combining Sodium Cocoyl Oat Amino Acids + Sodium Cocoyl Glycinate as a mild, non-irritating surfactant base.
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I am reading Handbook of Cosmetic Science and Technology, which is quite old (2001). It says that although the precise mechanism is unknown, the suspected mechanism is formation of larger and more stable micelles of surfactants (in the system containing several surfactants). They say although addition of amphoteric surfactants, demonstrate the most obvious result, non-ionic and even some anionic lead to a milder product. Since smaller micelles are more irritating, I guess that theory sounds reasonable.
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Thanks @ngarayeva001
I’ve never actually researched the topic, but that would seem to be a very plausible explanation.
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You are welcome @MarkBroussard. This is the book I was referring to in case you would like to see more details:
Starting from page 271.
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@ngarayeva001 thank you, I will check this out.
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@MarkBroussard thank you for the reply. We are uncertain if he has some type of oat allergy however I will look into Sodium Cocoyl Glycinate.
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