Glycolic Acid (0.5%)
Glycolic acid is an alpha-hydroxy acid (AHA) — the smallest and simplest of the AHA family — with CAS number 79-14-1. It occurs naturally in grapes, sugar cane juice, sugar beet, and Virginia creeper leaves, but the cosmetic-grade version is most often synthetic. Its effectiveness is highly dependent on both concentration (typically 4–20% for at-home use) and formulation pH (optimal range 3–4), as it loses efficacy above pH 5.
Glycolic acid gently lifts dead skin cells to reveal fresher, smoother skin with near-immediate visible results. With longer-term use it has demonstrated the ability to stimulate collagen synthesis (leading to firmer skin over 4–6 months) and to disperse melanin, helping to fade sun-induced brown spots and post-inflammatory hyperpigmentation (PIH). It also increases skin thickness and improves penetration of other skincare actives.
Increases skin sensitivity to UV radiation — daily broad-spectrum sunscreen use is essential. Stinging or burning is possible, especially at higher concentrations; over-exfoliation (visible peeling, redness, irritation) should be avoided by starting infrequently and increasing gradually. Not recommended for very sensitive or rosacea-prone skin; BHA or PHA alternatives are suggested in those cases. Concentrations above 20% are considered professional/clinical territory.
