We thank Drs Coleman and Brody for their letter regarding our study. Since glycolic acid peeling solutions are used in a variety of strengths, the term "low-strength" might have been a useful addition to our title. It is true that we purposely chose lower concentrations of glycolic acid to peel our patients, in order to avoid visible frosting or epidermolysis. This latter reaction frequently leads to postinflammatory hyperpigmentation in our experience, which then requires weeks or months of depigmenting agents afterwards. Previous studies have reported that 50% to 70% glycolic acid peels can cause depths of injury equal to 30% to 50% trichloracetic acid peels,1 a response we were trying to avoid in these patients with skin types IV and V. The erythema produced in our patients indicated a biologic effect, but fortunately was not severe enough to cause postinflammatory hyperpigmentation. Use of glycolic acid has been shown to decrease keratinocyte cohesion down to the granular cell layer,2 which we hoped would enhance the penetration of hydroquinone. Unfortunately, we did not even detect a trend in improvement of melasma after 4 peels. Dermatologists taking care of brown-skinned patients worldwide face a daily dilemma in which they are asked to remove pigmentation without going too far. This balancing act will continue until we have more effective therapies as a result of additional, controlled, prospective studies.
Hurley ME, Guevara IL, Gonzalez RM, Pandya AG. Efficacy of Low-Strength Glycolic Acid Application in the Treatment of Melasma—Reply. Arch Dermatol. 2003;139(6):811–812. doi:10.1001/archderm.139.6.811-a
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