Epidermal and dermal effects of topical lactic acid.

BACKGROUND Many alpha-hydroxy acid products, containing low- or high-acid concentrations, are being used. It is not known whether different products perform differently or whether they modulate changes in both the epidermis and dermis. OBJECTIVE The purpose was to examine whether treatment with 5% and 12% lactic acid produces different cosmetic results and produces changes in the epidermis and dermis. METHODS Test participants applied either 5% or 12% lactic acid twice a day for 3 months. Changes in skin smoothness and texture, the depth and number of lines and wrinkles, and epidermal and dermal firmness and thickness were determined. RESULTS Treatment with 12% lactic acid resulted in increased epidermal and dermal firmness and thickness and clinical improvement in skin smoothness and in the appearance of lines and wrinkles. No dermal changes were observed after treatment with 5% lactic acid; however, similar clinical and epidermal changes were noted. CONCLUSION The results demonstrate that cosmetic benefits from the use of alpha-hydroxy acids are caused by modification of the skin surface, the epidermis and the dermis. Although 5% lactic acid modulates surface and epidermal changes, 12% lactic acid influences both the epidermis and the dermis.