LACK OF PHOTOTOXICITY OF COSMETIC FORMULATIONS CONTAINING GLYCOLIC ACID IN AN IN VITRO HUMAN SKIN MODEL.

Glycolic acid (GA) is a naturally occurring product found in sugar cane and is a member of a class of chemicals known as alpha-hydroxy acids. GA has been widely used in cosmetic and dermatological formulations for over a decade. These formulations are often used in dermal applications where they may be sub-ject to ultraviolet radiation (UV) exposure from sunlight. We have investigated the potential for phototoxicity of typical cosmetic concentrations of GA. (4% and 8%) in a generic cosmetic formulation with and without a chemical sunscreen (octyl methoxycinnamate, SPF2). The assays were conducted following a cytotoxicity protocol using a human keratinocyte model, EpiDerm™ (Epi-200), utilizing a colorimetric thiazolyl blue (MTT) endpoint. Prior to formulation exposure, a maximum non-cytotoxic dose in EpiDerm was established for UVA/B radiation (290-400nm) utilizing a metal-halide amp solar simulator. The maximal dose of UVA/B radiation that caused negligible cytotoxic effects was 1.35/ 0.135 J/cm2 UVA/UVB, respectively. The maximal exposure for UVA treatment alone (320-400nm) was 6 J/cm2. For subsequent assays, EpiDerm cultures were treated with the maximal noncytotoxic dose of UVA/B or UVA. EpiDerm cultures were exposed to test materials or controls (negative control, vehicle; positive control, chlorpromazine) for two hours prior to UV exposure and returned to the incubator (0-45 hours) after exposure, followed by MTT cytotoxicity analysis. GA treated tissues exposed to UV showed relative survival percentages comparable to tissues that received no UV (89-109%); positive phototoxic control showed an expected cytotoxic response (7.5%). These studies indicate that glycolic acid contained in these cosmetic formulations is not phototoxic after UVA/B or UVA exposure and can be used in dermal cosmetic applications where UV radiation exposure may occur.

AHA, Alpha hydroxy acids, EpiDerm, MTT, MTT ET-50 tissue viability assay, MTT assay, Phototoxicity, Sun screens, UV light, UVA, UVB, Ultraviolet radiation (UV)