Surfactant

This group of ingredients helps the water mix better with sebum, makeup residue, and dirt to make them easier to remove when washing. This effect is due to the fact that surfactant molecules reduce the surface tension of the liquid and work at the boundary of water and oils, improving the wetting, cleansing and distribution of the product over the skin and hair. That is why they are important not only in washing gels and shampoos, but also in micellar water, foams, shower products and some cream formulas, where they help to stabilize the mixture of water and the oil phase. (britannica.com)

In cosmetics, such substances affect several properties of the product at once: they create foam or, conversely, regulate its amount, improve its cleansing ability, make the texture more homogeneous and help the formula not to exfoliate. For hair, this is especially important in shampoos.: Surfactants help to remove sebum, dust and styling from the surface of the hair and scalp. At the same time, the mildness of the action depends on the specific ingredient and its concentration, so some cleansers are suitable even for frequent use, while others may feel more intense. Typical examples include Sodium Laureth Sulfate and Cocamidopropyl Betaine; the former is often responsible for pronounced cleansing and foaming, while the latter is often used to soften formulas. The FDA also notes that some cosmetic ingredients in this group may be detergents, foaming and emulsifying ingredients. (fda.gov)