Substance typically found in plant and animal lipids (fat). Fatty acids include compounds such as glycerides, sterols, and phospholipids. They are used in cosmetics as emollients, thickening agents, and, when mixed with glycerin, cleansing agents. Fatty acids are natural components of skin and are components of a complex mixture that makes up the outermost layer that protects the body against oxidative damage (Sources: Free Radical Research, April 2002, pages 471–477; and Journal of Lipid Research, May 2002, pages 794–804). Fatty acids can help supplement the skin’s intercellular matrix. See natural moisturizing factor (NMF)