An alpha hydroxy acid extracted from milk. It is the only alpha hydroxy acid that occurs as a natural metabolite of healthy skin cells, so it doesn't irritate the skin like glycolic acid. Lactic Acid exfoliates cells on the surface of skin by breaking down the material that holds skin cells together. Although lactic and glycolic acids both have similar characteristics that cause exfoliation, lactic acid is a three-carbon chain, whereas glycolic acid is a two-carbon chain. As a two-carbon chain, glycolic acid reacts more rapidly, is usually harsher and more irritating to the skin, and it is more likely to cause unwanted complications. Lactic acid is unique in its proven ability to boost the skin's immune system and to help prevent abnormal precancerous growth. Because it is a superb humectant -- lactic acid attracts skin’s existing water molecules to the surface, which stimulates the growth of new collagen and elastic fibers in the dermal layer of the skin. Over a period of time, the skin surface will begin to look younger and smoother. Lactic acid also enhances the absorption of other substances, which allows the collagen in the Soapless Soap formula to further penetrate cellular structure.