This medication works in two ways. First, it goes after bacteria, which are crucial in the development of acne. Without bacteria, the sebum trapped under the skin would not become the fatty acids that cause all the swelling and inflammation in and around acne blemishes. Second, some studies show that benzoyl peroxide may also peel the dead skin cells from inside your hair follicles, to keep plugs from forming. These older medications tend to work mostly on the surface of your skin to help heal existing blemishes by unclogging pores.
Salicylic acid is particularly effective on blackheads.
Topical antibiotics These medicines are used by doctors to treat certain kinds of acne, such as postules and papules, but they may not be strong enough to have an effect on larger cysts. Topical antibiotics work by attacking the bacteria that are strongly linked with acne problems. Like other topical treatments, these tend to dry and irritate the skin, so be sure to use proper cleansing and moisturizing. Like benzoyl peroxide, retinoic acid works by peeling skin cells from the hair follicles so that plugs do not form. Be warned that at first it may aggravate your acne, and that it can take two to three months for any real improvement.