Duac once daily gel contains two active medicines called clindamycin and benzoyl peroxide which belongs to a group of medicine known as anti acne preparations duac once daily gel is used for the treating of mild to moderate acne on your skin the clindamycin is an antibiotic which stops the bacteria involved in the acne from reproducing whilst the benzoyl peroxide reduces blackheads and whiteheads and also kills the bacteria involved in acne used together in duac gel these work by fighting