Citric Acid (100 Ppm)
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, chelating, and masking agent in cosmetic formulations. While it is technically an exfoliant, it is most commonly used in small amounts to adjust the pH of a formulation rather than as a primary exfoliating active.
Citric acid can gently lift 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 high concentrations it may cause irritation, though it is typically used at low levels in most formulations.
