| Make sure that you wash your hair, and condition it before you wash your back. Conditioner is extremely comedogenic, and will clog pores. I always wash my back last.
Find a good back scrub, one that reaches all the way around. It's very hard to exfoliate your back when you shower, it's not an easy to reach place, but exfoliation is the key to good skin; those dead skin cells on your back are definitely not helping the breakouts.
Always wear a clean shirt to bed, and change your sheets often.
Benzoyl peroxide is good, too. If you do use it, be sure to use it generously, as the skin is a lot thicker on your back than your face. You can also get some prescription antibiotics to clear up body acne, as well... minocycline is extremely popular for this reason, as is tetracycline.
Good luck |