Reticulate hyperpigmentation of the skin after topical application of benzoyl peroxide.

Sir, Benzoyl peroxide (BP) is an e¡ective and frequently used topical medication for the treatment of acne vulgaris. It is a strong, broad spectrum bactericidal agent that signi¢cantly decreases the number of Propionibacterium acnes in both the follicle and on surface skin (1). A common side e¡ect after usage is irritation of the skin, usually manifested as a stinging or burning, and sometimes accompanied by erythema and scaling. Benzoyl per-oxide is a strong irritant, but a weak allergen, rarely causing a contact dermatitis (2, 3). Tolerance can be achieved by gradually increasing the frequency of application over time. We describe two cases in which topical application of benzoyl peroxide resulted in an unusual pattern of reticulate hyperpigmentation of the skin, most likely as a sequela of an irritant contact derma-titis. CASE REPORTS Case 1 A 29-year-old African-American man applied 5% benzoyl peroxide gel twice daily to the trunk for the treatment of acne vulgaris. The patient had no history of previous use of benzoyl peroxide. After 1 week of use, a bright erythematous, scaly eruption developed at the sites of application on the trunk. After discontinuing the benzoyl peroxide, the eruption resolved leaving a ¢ne lacy reticulate pattern of dark brown hyperpigmentation across the trunk and shoulders (Fig. 1). A skin biopsy specimen revealed ¢ndings consistent with postin£ammatory hyperpigmentation. A 31-year-old African-American man was treated for acne with 5% benzoyl peroxide gel twice daily to the trunk and face. The patient had no history of previous use of benzoyl peroxide. He subsequently developed an erythematous, scaly rash at the sites of application on the upper trunk; his face remained clear. He discontinued the benzoyl peroxide, and, over the next several weeks, a ¢ne lacy reticulate pattern of dark brown hyperpigmentation developed over the upper trunk. A skin biopsy specimen revealed ¢ndings consistent with postin£amma-tory hyperpigmentation. DISCUSSION Benzoyl peroxide is produced in 2.5, 5, and 10% strengths and can be applied as a gel, lotion, cream or wash. Its most common use is in acne vulgaris, although it has been recommended for use in a variety of other dermatoses (4). Although it is an uncommon sensitizer, its application is often irritating. Haustein et al. (3) reported on the irritant potential of benzoyl peroxide. Eleven of 155 acne patients had clinical signs of intolerance on the face, which settled despite continued use in 10 cases. Twenty-nine percent of acne patients and non-exposed …