The most common (and most useful) ingredients in body acne cleansers deliver a one-two punch: One ingredient puts P. acnes on the ropes, and the other keeps it there. These are found in separate products, so you can alternate using them.
The first ingredient to look for is benzoyl peroxide. A chemical relation to hydrogen peroxide, benzoyl peroxide kills P. acnes by drowning it with oxygen. (The bacteria are anaerobic, which means they thriving in oxygen-free environments.) A concentration of around 2 percent is typical, with 10 percent found in maximum strength formulas.
The second ingredient is a mild stripping agent called salicylic acid. Salicylic acid, which occurs naturally in willow trees, breaks down a skin protein called keratin. As the keratin dissolves, it takes a lot of the dirt and dead cells with it. Concentrations range from 0.5 percent to 2 percent.
Despite their low doses, both of these chemical compounds can dry and irritate skin. It's wise to start on the low end and increase concentration only if necessary. If you're concerned about skin sensitivity, choose formulas made without dyes or fragrances, especially synthetic ones. Some brands include skin softeners like aloe and allantoin.
Likewise, avoid other skin care products with alcohol, abrasive granules, or deodorant or antibacterial chemicals, all of which can dry out skin. Also steer clear of products that contain oil. If you need a moisturizer to offset the effects of the cleanser, check for products marked "oil-free," which contain other sealants to help skin retain its natural oil, or "noncomedogenic," which are designed to keep pores from clogging.
Now that you know what should be on the outside of the package, what sort of product should be inside? Next, we compare the different delivery systems for cleansing acne-prone skin.