Alpha Hydroxy Acids (aka. AHA) are acids that are commonly derived from fruits (citric, malic and tartaric acid) but can also come from milk (lactic acid), or sugar (glycolic acid). Alpha hydroxy acids are also widely synthesized for cosmetic use. AHAs work as exfoliants by essentially dissolving the glue that holds dead skin onto the surface. When used as an exfoliator, concentrations should be at least 4%, at a pH between 3 and 4.
Because AHAs work to expose new skin, users will be more sensitive to the damaging effects of the sun. Use of a daily sunscreen is an imperative part of any routine that includes AHAs.