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Penetration Enhancers in Cosmetics
From my point of view, penetration enhancers don’t really contribute all that much to cosmetics. Considering that moisturizers and the like do most of their work on the surface layers of the skin, it doesn’t seem all that useful. After all, some of the most effective moisturizers on the market are simple ointments with nothing more than glycerin and petrolatum. Most importantly, even if penetration enhancers made a slight difference, I highly doubt that consumers would be able to notice it. With that being said, I am still a university student and I don’t have the extensive experience of others on this forum, so I’m interested in hearing from you guys.
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12 Replies
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You step into drug category with penetration enhancers because as you mentioned cosmetics should stay on the surface. Also, it’s not as straightforward as adding DMI or propylene glycol and hoping your active ingredient would perform better. The entire formula matters.
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ngarayeva001 said:You step into drug category with penetration enhancers because as you mentioned cosmetics should stay on the surface. Also, it’s not as straightforward as adding DMI or propylene glycol and hoping your active ingredient would perform better. The entire formula matters.That’s what I gathered. Having the right actives at the right concentrations will always be the most important aspect of formulation. Penetration enhancers have always struck me as something that’s only really relevant in pharmaceuticals.
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You mention glycerol and petrolatum… these alongside many other common ingredients can serve as penetration enhancers, are likely to be considered ‘actives’, and penetration depth does matter with these.Every molecule (active or not) has its own requirements regarding how to enhance penetration. As an example: petroleum jelly will act as penetration enhancer for salicylic acid.Things also depend on your definition of ‘actives’ and ‘penetration enhancer’. Lecithin and ceramides can be considered actives especially if delivered deep enough into the skin. Therefore, they may profit from penetration enhancers (which won’t be solvents like DMI or PG) or penetration enhancing formulations. The cool thing about lecithin is that it can be formulated as liposomes which transforms this excipient into a penetration enhancer, not just for actives but also for itself (if you get what I mean).
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@natzam44, [disclaimer this is semi-anecdotal semi-confirmed] for example retinol (I am refering to INCI retinol not retinoids in genereal) is much more offensive in o/w emulsion than in anhydrous vehicle. And this works no matter whether you add penetration enhansers to that o/w or not. So, it’a about the formula as a whole. Also, don’t listen to what consumers say they “want”. Majority of consumers will freak out if you give them retinol that actually “does something”. The more active the ingredient is, the more irritation it will cause (in most cases). People want gain without pain, so big companies just stick retinyl palmitate (that has no proven effect on skin but conveniently doesn’t cause irritation as other derivatives do) to their products and call it a day. L’oreal reformulated C E Ferulic when they bought SkinCeuticals because 20% of LAA stings and burns and people don’t like it.
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@ngarayeva001 @Pharma Thank you both for the insight.
I’m certainly still partial to @ngarayeva001 ‘s point of view mostly due to the fact that consumers are a rather confused bunch. In the years since I’ve started formulating, I have seen people swear by all sorts of odd (and possibly dangerous) treatments which had no basis in reality. Although this is anecdotal, it would seem that humans simply aren’t attentive enough to notice subtle changes.
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Pharma said:You mention glycerol and petrolatum… these alongside many other common ingredients can serve as penetration enhancers, are likely to be considered ‘actives’, and penetration depth does matter with these.Every molecule (active or not) has its own requirements regarding how to enhance penetration. As an example: petroleum jelly will act as penetration enhancer for salicylic acid.Things also depend on your definition of ‘actives’ and ‘penetration enhancer’. Lecithin and ceramides can be considered actives especially if delivered deep enough into the skin. Therefore, they may profit from penetration enhancers (which won’t be solvents like DMI or PG) or penetration enhancing formulations. The cool thing about lecithin is that it can be formulated as liposomes which transforms this excipient into a penetration enhancer, not just for actives but also for itself (if you get what I mean).
@Pharma how and why petrolatum enhances the penetration of salicylic acid?
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Occlusion and insolubility
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@Pharma does any occlusive and insoluble ingredient enhance the penetration of other ingredients or just petrolatum?
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Both phenomena are not bound to petrolatum but anything with such properties. You can achieve occlusion with a cling film. The insolubility or ‘anti-solvent’ part highly depends on the ingredient and its solubility and insolubility in different solvents and its solubility in skin.
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@Pharma But wouldn’t the insolubility of the active make it almost impossible to diffuse inside the vehicle, after the frontline get absorbed?Ultimately, only the first few lucky guys get into skin thanks to petrolatum, and all the others get blocked out by the petrolatum left by the lucky ones.
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@zetein Most likely they won’t be blocked because the molecules of SA will diffuse down a concentration gradient from the vehicle ( high concentration) to SC(lower concentration) while Petrolatum will remain on the surface of skin providing occlusion.
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