Benzoyl peroxide for acne treatment is typically applied to the affected areas in gel or cream form, in concentrations of 2.5% increasing through the usually effective 5% to up to 10%. Research suggests that 5 and 10% concentrations are not significantly more effective than 2.5%, and 2.5% is usually better tolerated, though the majority of major studies comparing it to other treatments use the higher concentrations. It commonly causes initial dryness and sometimes irritation, although the skin develops tolerance after a week or so. A small percentage of people are much more sensitive to it and liable to suffer burning, itching, peeling and possibly swelling. It is sensible to apply the lowest concentration and build up as appropriate. Once tolerance is achieved, increasing the quantity or concentration and gaining tolerance at a higher level may give better subsequent acne clearance. Benzoyl peroxide works as a peeling agent, increasing skin turnover and clearing pores, thus reducing the bacterial count there as well as directly as an antimicrobial. It is often combined with salicylic acid, sulfur, erythromycin or clindamycin (antibiotics), giving rise to a combination drug, in benzoyl peroxide/clindamycin. It can also be given with adapalene (a synthetic retinoid) in adapalene/benzoyl peroxide, a unique formulation considering most retinoids are deactivated by peroxides and acids.
In the U.S., the typical concentration for benzoyl peroxide is 2.5% to 10% for both prescription and over-the-counter drug preparations that are used in treatment for acne. Higher concentrations are used for hair bleach and teeth whitening. Benzoyl peroxide, like most peroxides, is a powerful bleaching agent. Contact with fabrics or hair can cause permanent color dampening almost immediately. Even secondary contact can cause bleaching. For example, contact with a towel that has been used to wash off benzoyl peroxide-containing hygiene products. In the paint industry, Benzoyl peroxide is used as hardener in order to start the polymerization process in resins for instance PMMA resins can be polymerized with DiBenzoyl Peroxide.