Part of an effective butt acne cure regimen includes gently exfoliating the affected areas, by using a loofah or acne cleansing sponge to lightly wash your bottom, as opposed to abrasively scrubbing it.
Be sure to shower as soon as possible after perspiring heavily. Also, while exercising or doing other physical activities which cause you to sweat, be sure to wear cotton clothing that fits loosely. This will allow your skin to get more air and hinder the development of acne in undesired places, like your behind!
Do not pick or squeeze the pimples on your butt, this will cause them to become infected.
Follow an effective skin care regimen for your behind, just as you would your face. Note, the key word here is effective. So find one that actually works.
If you have a bunch of red or white bumps all over your butt, and possibly the legs too, that seems to be a little hard pimple rash, but you're not really sure. It could be a condition called - Keratosis Pilaris. This condition develops when hair follicles become blocked and get inflamed because of the over reproduction of keratin proteins in the skin cells. This causes bumps to develop which usually seem to be worse in the winter months, more so than in the summer months. Also your doctor can prescribe Erythromycin 2% to help with the symptoms, but it probably won't clear it up completely in most cases. Be sure to inquire about this type of butt acne at your next doctor's visit.