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Benzoyl peroxide (or BP, as it’s affectionately known) is one of those products that seems to work for everyone. It’s a topical treatment (cream) that’s an essential component of many acne treatment regimens (Dan Kern’s acne.org, ProActiv, Paula Begoun just to name a few). But what does it do, and how is it most effective?
Benzoyl peroxide is a peroxide, much like hydrogen peroxide, which is the peroxide of peroxide blondes. In chemistry, peroxide refers to the two oxygen atoms linked together. This is an unstable bond which readily breaks up into free radicals:
At the moment, benzoyl peroxide’s mechanism of action is not completely understood, but it’s thought that the free radicals kill bacteria that contributes to acne, Propionibacterium acnes, by interacting with their cell walls (their “skin”). Additionally, it seems to encourage peeling, which helps stop pores from getting clogged, which is the first part of the acne-forming process.
However, benzoyl peroxide has a number of not-so-nice side effects, including dermatitis (either from irritation which gets better after about a week, although about 1% of people can have a true allergic reaction to it) and bleaching of fabric and hair.
Benzoyl peroxide can be commonly found in concentrations between 2.5 and 10%. To minimise side effects, lower concentrations can be used. A few studies have shown 2.5% benzoyl peroxide was as effective as stronger 5% and 10% formulations. Additionally, combining BP and antibiotics (e.g. erythromycin and clindamycin) can be a good way to increase effectiveness without also increasing reactions and antibiotic resistance.
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