Topical clindamycin plus topical benzoyl peroxide is more effective than topical clindamycin alone. Substances used are generally organic peroxides such as benzoyl peroxide or methyl ethyl ketone peroxide. Other options may include salicylic acid, coal tar, benzoyl peroxide, and phototherapy. Most formulations of tretinoin are incompatible for use with benzoyl peroxide. The use of topical benzoyl peroxide and antibiotics together is more effective than antibiotics alone. Benzoyl peroxide is in the peroxide family of chemicals. Benzoyl peroxide was the first organic peroxide prepared by intentional synthesis. Both regimens are effective, but benzoyl peroxide does not lead to antibiotic resistance. When used together with benzoyl peroxide products, temporary yellow or orange skin discolorations can occur. The carcinogenic potential of benzoyl peroxide has been investigated. MEKP and benzoyl peroxide are commonly used for this purpose. Some evidence suggests that benzoyl peroxide has an anti-inflammatory effect as well. It is also available combined with benzoyl peroxide under the brand names Epiduo and Tactupump. It consists of two benzoyl groups bridged by a peroxide link. An early method for production of benzoyl chloride involved chlorination of benzyl alcohol.