Benzoyl peroxide is a chemical compound (specifically, an organic peroxide) with structural formula  (C6H5−C(=O)O−)2, often abbreviated as (BzO)2. In terms of its structure, the molecule can be described as two benzoyl (C6H5−C(=O)−, Bz) groups connected by a peroxide (−O−O−). It is a white granular  solid with a faint odour of benzaldehyde, poorly soluble in water but soluble in acetone, ethanol, and many other organic solvents. Benzoyl peroxide is an oxidizer, which is principally used as in the production of polymers.As a bleach, it has been used as a medication and a water disinfectant. In specialized contexts, the name may be abbreviated as BPO. As a medication, benzoyl peroxide is mostly used to treat acne, either alone or in combination with other treatments. Some versions are sold mixed with antibiotics such as clindamycin. It is on the WHO List of Essential Medicines, and, in the US, it is available as an over-the-counter and generic medication. It is also used in dentistry for teeth whitening. Benzoyl peroxide is also used in the plastics industry and for bleaching flour, hair, and textiles. It is also used to remove stubborn stains from dolls and other plastic toys, although some users have claimed that the product has unwanted long-term effects of discolouring the item, particularly with the My Little Pony brand. History
Benzoyl peroxide was first prepared and described by Liebig in 1858.
Toxicity
Benzoyl peroxide breaks down in contact with skin, producing benzoic acid and oxygen, neither of which is very toxic.The carcinogenic potential of benzoyl peroxide has been investigated. A 1981 study published in the journal Science found that although benzoyl peroxide is not a carcinogen, it does promote cell growth when applied to an initiated tumor. The study concluded, "caution should be recommended in the use of this and other free radical-generating compounds".A 1999 IARC review of carcinogenicity studies found no convincing evidence linking BPO acne medication to skin cancers in humans. However, some animal studies found that the compound could act as a carcinogen and enhance the effect of known carcinogens. Skin irritation
In a 1977 study using a human maximization test, 76% of subjects acquired a contact sensitization to benzoyl peroxide. Formulations of 5% and 10% were used.The U.S. National Institute for Occupational Safety and Health has developed criteria for a recommended standard for occupational exposure to benzoyl peroxide. Cloth staining
Contact with fabrics or hair, such as from still-moist acne medication, can cause permanent color dampening almost immediately. Even secondary contact can cause bleaching, for example, contact with a towel that has been used to wash off benzoyl peroxide-containing hygiene products. Reactivity
The original 1858 synthesis by Liebig reacted benzoyl chloride with barium peroxide, a reaction that probably follows this equation:

2 C6H5C(O)Cl + BaO2 → (C6H5CO)2O2 + BaCl2Benzoyl peroxide is usually prepared by treating hydrogen peroxide with benzoyl chloride under alkaline conditions.