Benzoyl peroxide is a compound made from hydrogen peroxide and benzoyl chloride. The ingredient is known to effectively kill the bacteria that causes acne and to remove excessive oil and dead skin cells at the same time 1,2. Benzoyl is therefore suitable for blackheads as well as pimples.
Before using a product that contains benzoyl peroxide for the first time, one should apply it on a few affected areas for a couple of days to see if it causes skin irritation. It is not unusual to see an initial and transient redness and scaling of the skin, but this should subside after some time3. Further, benzoyl peroxide can make the skin more sensitive to the sun, and you should be careful when applying it, also beware that benzoyl peroxide can bleach both hair and clothing.
Studies show an antibacterial effect (targeting the bacteria causing acne) as well as a mild anti-inflammatory effect4.
Older studies using 5% benzoyl peroxide have shown this to have at least similar effects on measures of acne severity when comparing with topically applied formulations with antibiotics such as clindamycin5 and erythromycin6, which are standard treatments in acne.
Benzoyl peroxide seems to have the biggest effect in combination with other ingredients such as azelaic acid7.
The concentration of benzoyl peroxide in products typically varies from 2.5% to 10%, and the strength should depend on which area on the body it is applied. Benzoyl peroxide in concentrations less than 5 % can be used on the face, while stronger concentrations are generally reserved for chest and back8. In general, lower concentrations (eg. 2.5-5%), water-based and wash-off products might be better tolerated in patients with more sensitive skin9.
The concentration of an ingredient is important for its efficacy, and therefore products containing the same ingredient may not necessarily have the same effect as in the studies mentioned above.
Updated: July 2017