Emulsifiers, also known as stabilizers, are ingredients that allow two immiscible ingredients to coexist and have a unified distribution in a product. Essentially, an emulsifier is something would allow combinations like oil and water to both be in a product, without having that product separate (Minister of National Health).
A thickener is an ingredient that changes the consistency of a product, making it more stable and increasing viscosity. Many thickeners also have emulsifying properties. There are gelling and non-gelling thickeners which alter the consistency of the final product in a way concurrent with their
names (Making Cosmetics).
Emulsifier: Lecithin
Lecithin is a combination of amino acid and choline naturally found in the liver but can be made synthetically using soy (Huntingdon College of Health Sciences). It’s also found in egg yolks and wheat germs. It’s combination of polar and non-polar properties make it function as an emulsifying agent (Elmhurst).
Lecithin has been found safe in wash-out products and in leave-in products at a concentration of up to 15%. It’s been found virtually nontoxic, but because it could form nitrosamines, it should not be used with products containing N-nitroso (International Journal of Toxicology).
Lechithin is a lipsome that’s excellent for delivering other ingredients into the skin with minimal irritation (Skin Pharmacology). But that also means it shouldn’t be paired with any ingredient that shouldn’t be absorbed into the skin (International Journal of Toxicology).
Thickener: Beeswax
Beeswax is a commonly used, non-gelling thickener that’s a kind of wax ester (Skin Therapy Letters). It also has some emollient qualities. In combination with honey and olive oil, beeswax has been shown to reduce dermatitis and psoriasis.
Tests have shown that it’s generally safe (International Journal of Toxicology).
Both: Cetearyl Alcohol
Cetearyl Alcohol is one of the 5C’s of alcohol — that is, the alcohols that are actually moisturizing to skin and hair. It comes from vegetables and is a combination of stearyl and cetyl alcohols. It’s used as a co-emulsifier along with lactylates, but it works primarily as a thickening agent (The Herberie).
It’s been found to be nontoxic and is often used in both hair and skin care formulas, with hair care formulas containing up to 20% cetearyl alcohol.
Bottom Line
Emulsifiers and thickeners are a crucial part of cosmetics. They can either allow dissimilar ingredients to be delivered together or make the consistency of a product thicker and more user-friendly.