BP works in several different ways. First, it acts as an antimicrobial agent. The bacteria that is most commonly linked to acne breakouts, Propionibacterium acnes, is considered to be mostly anaerobic, meaning it thrives best in an environment with little oxygen. Benzoyl peroxide provides oxygen to the pores, therefore hindering the growth of the bacteria. I should mention that while acne bacteria typically favors limited oxygen in its environment, the bacteria can be more/less tolerant of oxygen depending on the patient. BP also acts to peel the layers of the skin, decreasing the amount of time the skin takes to heal and build a new, healthy layer.
Definitely, over using any active can cause irritation and hurt more than it helps. BP is a drying agent used in skin care. Any professional skin care specialist will tell you that using too much benzoyl peroxide will dry out your skin too much. If you decide to use this product, do not use it on your entire face because it will definitely dry out your skin too much. When that happens, your oil glands kind of go into over drive and start creating excess oil to make up for the dryness. Another side effect of benzoyl peroxide is having flaky, red skin along with being oily.