Benzoyl peroxide is available in the form of creams (containing 4, 5 and 10 per cent), a gel (5 per cent) and a wash (5 per cent).

There is little difference in response to the different concentrations in terms of reducing inflammatory lesions, but formulation appears to make a difference; the drying effect of an alcoholic-gel base enhances the effectiveness of the active constituent, for example. However, the gel is more likely to cause drying of the skin and irritation than bland aqueous bases.

The 4 per cent cream is formulated in a hydrophase base; the manufacturer claims that this formulation holds the benzoyl peroxide in solution, increasing its bioavailability and reducing irritation.

Potassium hydroxyquinoline sulphate, which has antibacterial and keratolytic properties, is co-formulated (at 0.5 per cent) with benzoyl peroxide (5 and 10 per cent) in two cream formulations.