Foaming

Such ingredients help the product to form a foam quickly upon contact with water and spread more evenly over the skin or hair. Most often, these are surfactants.: they reduce the surface tension of water, improve the wetting of impurities and make it easier to remove them when washing, shampooing or cleansing the body. Due to this, the product is perceived as more "washing", and its texture seems light, airy and convenient to use. This is especially important for hair in shampoos: foam helps to better distribute the composition along the length and scalp, although it does not determine the cleansing power by itself. Definitions of cosmetics and cleaning products, as well as the role of such ingredients in formulas, are confirmed by the materials of the FDA and the CosIng database. (fda.gov)

In cosmetics, this function is found primarily in shampoos, shower gels, face washes, and liquid cleansers. Typical examples are Sodium Laureth Sulfate and Cocamidopropyl Betaine: the former is responsible for active foaming and good cleansing, the latter is often added for more soft foam feeling and improved sensory properties of the formula. The FDA also notes that some diethanolamine derivatives can be used in cosmetics as foaming agents, and CIR reviews indicate that Sodium Laureth Sulfate is widely used in shampoos and other washable products. For sensitive skin, overly active cleansing systems can sometimes cause dryness or irritation, so comfort depends not only on the presence of foam, but also on the overall softness of the entire formula. (fda.gov)