When acne forms on the buttocks, it's because of folliculitis. Folliculitis is usually caused when the Staphylococcus aureus, or staph bacteria, infects a hair follicle. Normally staph bacteria live on your skin without causing problems, but when they get inside through a break in the skin, it results in infection. It can b treated with proper medications. Consult a Dermatologist fort he same.
Health Tips
Avoid tight fitting clothes and undergarments. Use a medicated anti fungal powder