ABSTRACT
BENZOYL PEROXIDE Benzoyl peroxide (BPO), a mainstay treatment of mild to moderate acne for decades, has mainly antimicrobial, anti-inammatory effect and only mild anticomedogenic effects. Acting through oxidation and formation of free radicals, its bacteriostatic activity is superior even to that of topical antibiotics (3). It decreases inammation by killing polymorphonuclear leukocytes (PMNs), preventing the release of reactive oxygen species (4). The mild keratolytic activity is probably linked to the destruction of P. acnes. Indeed recently it has been shown that P. acnes is able to increase the proliferation and modulate the differentiation of keratinocytes, thus playing a role in the formation of the comedo (5). Unfortunately, oxidative destruction of the SC may deplete cutaneous vitamin E, resulting in oxidation of surface lipids and proteins; this may predispose to skin dryness and desquamation (6). BPO is absorbed effectively into the epidermis, particularly by pilosebaceous units, and converted to benzoic acid, with approximately 2% entering the systemic circulation (7,8). Its lipophilicity allows it to enter and accumulate in the lipid-rich pilosebaceous units and subcutaneous fat (4). It is an FDA Pregnancy Category C agent, with little known about potential fetal harm or breast milk excretion, and positive in the rodent photocarcinogenicity assay. In Europe, it can be prescribed to pregnant women. It is widely available both over the counter (OTC) and by prescription, and comes in different concentrations ranging from 2.5% to 10%. Adverse effects include dryness, peeling, burning, and redness of skin, with contact allergy only in 1% to 2% of patients (3). To that end, patients should avoid excessive UV radiation, which can exacerbate irritation. Additionally, the water-based formulations may exert less drying, scaling, burning, and erythema than the alcohol-based formulations (3,9). Of note, BPO, an oxidizing agent, can bleach hair, clothing, and colored fabrics. It may also inactivate tretinoin if both are applied concurrently (10); in contrast, adapalene and tazarotene remain stable in the presence of BPO (7).
