Benzoyl peroxide is a topical medication that has bactericidal effects to reduce P. acnes. It is available in both over-the-counter (Table 7) and prescription formulations as a bar soap, wash, gel or lotion in varying concentrations. The stay-on formulations of benzoyl peroxide will decrease P. acnes counts more so than the washes although both significantly decrease P. acnes. The concomitant use of benzoyl peroxide with antibiotics will lessen P. acnes resistance to antibiotics and increase the bactericidal effect of the antibiotic (61). None of the topical antibiotics alone is more effective against P. acnes than benzoyl peroxide (27). Benzoyl peroxide products need to be used at different times of the day than tretinoin or tazarotene. Oxidation of these retinoids, and thus decreased efficacy, can occur when in contact with benzoyl peroxide. A benzoyl peroxide product may be utilized in the morning with night-time application of a retinoid. Caution should be given to the patient that benzoyl peroxide products can bleach linens and clothing. Benzoyl peroxide allergic contact dermatitis may happen but is rare with a 1:500 incidence (62).
There are several topical products that combine benzoyl peroxide with either erythromycin or clindamycin. These combination topical products treat inflammatory acne better than either product alone (63,64). The shelf-life for these combination products is limited; therefore, some formulations of erythromycin, and benzoyl peroxide need to be refrigerated. Diarrhea and pseudomembranous colitis are rare but have been associated with topical clindamycin.