A shortened form of "surface-active agent", a surfactant is a chemical that stabilizes mixtures of oil and water by reducing the surface tension at the interface between the oil and water molecules. Because water and oil do not dissolve in each other a surfactant has to be added to the mixture to keep it from separating into layers. Surfactants in cosmetics provide one or more of six functions:
- Detergents - for cleansing
- Wetting agents - in perms
- Foaming agents - for shampoos
- Emulsifiers - in creams and lotions
- Conditioning agents - in skin and hair-care products
- Solubilizers - for perfumes and flavors

