Placing on the World Health Organization's List of Essential Medicines, benzoyl peroxide is considered an essential chemical for any high quality health care system. It is a bridged peroxide link between two benzoyl groups, and is among the most important organic peroxides in terms of varied uses and applications, as well as the overall scale of its mass production. Primarily, benzoyl peroxide is used to reduce the effects and appearance of acne on the skin. The bactericidal effect on acne-causing bacteria initiated by benzoyl peroxide does not result in antibiotic resistance in the surface of the skin, making it ideal for regular treatment of skin conditions like acne. Combined with salicylic acid, sulfur, erythromycin, and clindamycin (a form of antibiotics), benzoyl peroxide is one of the most effective means of reducing or eliminating acne. Typically benzoyl peroxide acne treatments are applied as a cream or gel, usually in concentrations of 2.5%-5%. There are concentrations as high as 10%, though there is no evidence to support that higher concentrations are more effective than lower concentrations.