Acnecide contains the active ingredient benzoyl peroxide which attacks the bacteria (germs) known as Propionibacterium acnes, one of the main causes of acne. . Your doctor or pharmacist has recommended this medicine to treat your acne. Acne appears as blackheads and whiteheads which people often refer to as pimples or spots. . Acne of the face, chest or back may be treated with this medicine What Acnecide looks like and contents of the pack White to off white gel. Available in packs containing 40 g or 80 g ( 2 x 40 g) tubes. Please note that results may vary.