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Moisturizing cream
Hi formulators, when formulating a moisturizing skin product you often use both hydrophilic (glycerin) and hydrophobic(petrolatum) ingredients in the same emulsion/ formulation.(why?)
I can’t figure how that works on a molecular level. That glycerin attracts water and petrolatum lowers the TEWL is clear, but in the same emulsion? -
15 Replies
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I think glycerin is a good choice for high humidity conditions whereas in low humidity conditions it might draw the water from skin and there comes into play the best occlusive moisturizer known to us aka petrolatum. A balanced combination might prevent glycerin from drawing the moisture from deeper dermis while the petrolatum would act as a barrier to minimize the TEWL. But again it is appropriate for sort of dry conditions IMHO.
Hope someone can explain it better. -
In formulating a Moisturizer, you want to included ingredients with moisturizing properties such as hyaluronic acid, sodium lactate, sodium PCA, sorbitol, glycerin and moisturizing oils such as Meadowfoam, Argan and an occlusive or barrier film-former such as Petrolatum, Sclerotium Gum, etc. to reduce TEWL. The theory being that the moisturizing ingredients penetrate the dermis and draw/hold water and the film-former sits on the surface of the skin sealing it all in.
So, I would not think of it from hydrophilic / hydrophobic perspective, but from a function perspective. Yep, in the same emulsion … if you only had hydrophilic moisturizing ingredients, no need to make an emulsion. Same if you only had hydrophobic ingredients, no need to make an emulsion. -
Sounds correct both of you. But aren’t the water molecules penetrating the skin without help from glycerin? I mean we have the hydrophobic layer there to stop the water from evaporating so why glycerin? -
But I never heard the water molecules penetrating the lipid layer of skin????? Of course until and unless you have a specialty formula for penetration with a carrier/penetration enhancer.
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Ahh that’s true of course, but then you are saying (Mark) that glycerin penetrates the lipid layer of the skin and not water?
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I can only picture that the moisture you bring to the skin is the water in the formula - then a hydrophobic ingredient to seal it in.
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https://chemistscorner.com/how-do-skin-moisturizers-work/
She says humeactants take the water from the dermis up to the stratum corneum.. -
Here are some more insights…
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@david I think glycerin doesn’t cause any penetration it just maintain moisture at the surface of skin(hydrogen bond formation via 3oH groups) and petrolatum also maintains moisture(via barrier layer). why do u complicate it?
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Yes nasrins
I don’t know why I complicate it- however I got it now I think
humeactants/NMFs take the water from the dermis or from the cosmetic product to the stratum corneum and keeps it there, occlusives stops it from evaporatingHowever I would like to learn more about how the skin barrier works on a molecular level.Any literature suggestions? -
@david I have but now Im at home…
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Please also remember to make the distinction between the consumer feeling that she has moisturized skin, and her actually having moisturized skin. They are two different attributes, both equally important, but they are often achieved with different ingredient systems in the same formula.
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@bobzchemist take it easy…
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Humans are like tomatoes … we’re 98% water. You have two sources of moisture: water in the body and water in the atmosphere. You do your best to capture or bind the moisture and prevent it from evaporating.
@BobZ: Please elaborate -
Sorry if that came out sounding wrong - what I was trying to say is that the perception of having moisturized, soft skin is just as important as having skin with a higher water content.
The amount of atmospheric water that can actually be transported into/through the stratum corneum to affect the moisture content of the skin is minuscule. But…ingredients like humectants, gels and clathrates make the consumer feel as if her skin is being moisturized. And it’s that perception that drives sales and repeat sales. Even the best moisturizer in the world, if it does not feel moisturizing and elegant on the skin, and/or if the application of the product to the skin does not make the consumer feel good, will never be purchased a second time.
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