Benzoyl peroxide is primarily used in the treatment of acne vulgaris due to the antibacterial activity that these types of peroxides display. The drug is marketed under a variety of trade names in over 200 formulations. In treating patients with acne, the disappearance of acne coincides with the reduction of both the levels of P. acnes bacteria and free fatty acids. Benzoyl peroxide is absorbed in the skin where it is metabolized to benzoic acid and then excreted as benzoate in the urine. Side effects consist mainly of skin irritation including burning, blistering, crusting, itching, severe redness, and skin rash.