Benzoyl peroxide (BPO) has been used as an anti-acne treatment for several decades. Its unique activity is based on the ability to not only reduce Propionibacterium acnes, but also to decrease inflammatory lesions. As is well-known, P. acnes is the bacteria responsible for acne breakouts and it cannot live in an aerobic (i.e., oxygen-rich) environment. Benzoyl peroxide works by introducing oxygen into the pore, thereby killing the bacteria and, in turn, reducing the number of breakouts on the skin. And since BPO acts as a toxin on P. acnes rather than an antibiotic, resistance to BPO does not occur and has not been reported. Another factor that makes benzoyl peroxide so effective is its ability to help rid the follicle of excess dead skin cells since clearing the pore of cellular debris lessens the chances of pore blockages, or comedones. In this way, benzoyl peroxide helps to prevent breakouts before they start.