Glycolic acid is an alpha hydroxy acid (AHA) widely used in dermatology for the treatment of age spots (also known as liver spots or solar lentigines). Its mechanism of action is based on its keratolytic properties—it promotes the exfoliation of the stratum corneum by weakening the bonds between dead skin cells, thereby accelerating cell turnover. This process can lead to a more even skin tone and a reduction in the appearance of hyperpigmented lesions, including age spots.

Multiple clinical studies have validated the efficacy of glycolic acid in treating age spots and other forms of hyperpigmentation. Controlled trials and dermatological reviews (see references such as Journal of the American Academy of Dermatology, 1996; Journal of Dermatological Treatment, 2013) have shown that topical application of glycolic acid at concentrations typically ranging from 10% to 30% can lead to significant improvement in the color and size of age spots over several weeks to months. Glycolic acid is commonly used in chemical peels administered by professionals, as well as in over-the-counter formulations at lower concentrations.

The evidence supporting glycolic acid's use for age spots is robust, with both biochemical rationale and consistent clinical outcomes. It is considered a first-line topical therapy for mild to moderate photodamage and pigmentary disorders.