Citric Acid (11Ppm)
Citric acid is an alpha-hydroxy acid (AHA) derived from citrus fruits, with CAS numbers 77-92-9 / 5949-29-1. It functions primarily as a buffering and chelating agent in cosmetic formulations, and is also classified as an exfoliant. While it shares the AHA mechanism of gently lifting dead skin cells, it is most commonly used in small amounts to adjust the pH of a formulation rather than as a standalone exfoliant.
Citric acid can gently exfoliate dead skin cells to improve skin smoothness and freshness. Research suggests that with regular use at higher concentrations (around 20% over three months), it may help sun-damaged skin by increasing epidermal thickness and glycosaminoglycan content. However, comparative studies indicate it is less effective than glycolic or lactic acid for overall skin improvement.
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). At typical low concentrations used for pH adjustment, effects are minimal, but higher concentrations used for exfoliation warrant sun protection.
