Citric Acid
Citric acid is an alpha-hydroxy acid (AHA) derived from citrus fruits with the INCI CAS number 77-92-9 / 5949-29-1. It functions primarily as a buffering and chelating agent in cosmetic formulations, where it is most commonly used in small amounts to adjust the pH of a product. At higher concentrations (around 20%) and with regular use, it has been studied for its exfoliating and skin-improving properties, though comparative research suggests it is less effective than glycolic or lactic acid in this regard.
Citric acid can gently lift dead skin cells to smooth and refresh the skin surface. Research indicates that with regular use at higher concentrations, it may help improve sun-damaged skin, increase epidermal thickness, and boost glycosaminoglycan content in the skin. However, it is generally considered less potent than other AHAs such as glycolic or lactic acid for these effects.
As an AHA, citric acid may increase photosensitivity; the SCCS has issued position papers on the safety of alpha-hydroxy acids (opinions 0370/00 and 0799/04). Higher concentrations used for exfoliation may cause irritation, particularly in sensitive skin.
