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Common Cosmetic Ingredient Increases Photodamage By Ultraviolet Light

Topical glycolic acid, a representative alpha-hydroxy acid, sensitizes skin to the damaging effects of ultraviolet light.

Alpha-hydroxy acids are commonly used in cosmetics, explain investigators. Previous studies have suggested that they may increase skin's sensitivity to ultraviolet light. The researchers, from Ivy Laboratories in Philadelphia, Pennsylvania, Brookhaven National Laboratory in Upton, New York and the Food and Drug Administration in Washington, DC, United States, evaluated the effects of short-term topical treatment with glycolic acid in 29 Caucasian volunteers.

Glycolic acid 10% or placebo was applied to the backs of the volunteers once daily for 6 days per week. After 4 weeks, treated areas were exposed to 1.5 times the minimal erythema dose (MED) of ultraviolet light, which had been previously determined on untreated skin.

Sunburn cells were assessed in 16 subjects and cyclobutyl pyrimidine dimers in DNA were determined in 13 subjects. One week after discontinuing glycolic acid application, sunburn cells and MEDs were re-evaluated in the first group.

Results showed significantly increased sun burn cell induction and lowered MEDs after glycolic acid application compared with placebo. Cyclobutyl pyrimidine dimers were also increased with glycolic acid, but not to a statistically significant degree.

One week after discontinuation of glycolic acid application, sunburn cell induction and MEDs returned to the same level as the placebo group.

Short-term application of 10% glycolic acid enhances damage by ultraviolet light, the investigators conclude. This photosensitivity is reversed within one week of discontinuing treatment.
Photodermatol Photoimmunol Photomed 2003;19:1:21-27. "Topical glycolic acid enhances photodamage by ultraviolet light"

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