In my 10 years or so of working in cosmetic science I’ve learned a great deal. Having a foundation in biochemistry has been helpful since much of cosmetic science has to do with protein and lipids as well as biochemistry of skin. For those who are new, let me share a few definitions to help you get started.
Moisturizer – A substance or product that adds or restores moisture to the skin. Keep in mind that moisture refers to water so oils alone do not moisturize.
Humectant – A substance that binds to water to help retain moisture. This is important for the product itself to keep from drying out, but also to help keep the skin moistened. The best example is glycerin but humectants also include propylene glycol and sorbitol.
Emollient – A substance that softens and sooths the skin making it more supple. Typically this is an oil. It is thought to fill the crevices between the cells in the stratum corneum or outer layer of the skin to improve appearance.
Lubricant – A substance that reduces friction and often forms a film on the skin. This is important for feel when applying a product to the skin.
Barrier – Something that bars passage. Healthy skin is a barrier in that it bars passage of substances into and out of the body protecting it from the outer environment and holding moisture in. Lotions and creams help support this barrier function of the skin. Damaged skin is less of a barrier making it more prone to infection.
Occlusive – Impenetrable; a film spread on the skin to prevent moisture loss. Petroleum oil is one of the best occlusive agents but vegetable oils also work.
Emulsifier – Binds together substances that could otherwise not be mixed such as oil and water. Emulsifiers are used in any cream or lotion to help hold the oil and water phases together.
Surfactant – Reduces the surface tension of a liquid such as water. I first learned this word referring to a phospholipid that occurs in the lungs. Its function there is to reduce surface tension and help keep the lungs open for air to be there. In cosmetics it means the same thing but examples include detergents, foaming agents, emulsifiers and dispersants.
Antioxidant – A chemical that inhibits oxidation reactions or free radical damage to other molecules. Common antioxidants are vitamin A, C, and E and polyphenols. Antioxidants in skin care products are important both to protect the product itself as well as to diminish the signs of aging.
Preservative – A compount that inhibits the growth of bacteria and fungus or kills bacteria and fungus. Preservatives are important to protect the product itself as well as to protect the consumer from getting an infection that could be serious. It is absolutely necessary to to make sure products containing water or water based ingredients are properly preserved.
Exfoliant – Something that removes the outer, dead layer of skin cells, the stratum corneum. This can be done physically with an abrasive substance such as salt or ground seeds or chemically such as salicylic acid or alpha hydroxy acid.
Fixed Oils – Non volatile oils which are lipids or fats. They are sometimes used as a carrier for essential oils. These include olive oil, almond oil, etc.
Stratum Corneum – The outermost layer of the epidermis of the skin. It provides the skin with its barrier function.
Cosmeceutical – A combination of the words Cosmetic and Pharmaceutical. It refers to a cosmetic ingredient that has a pharmacetical action on the skin. The term is not recognized by the FDA and a cosmetic that makes a pharmaceutical claim is no longer considered a cosmetic but rather an over the counter drug.