There are many reasons for back acne, generally consider folliculitis, acne and other diseases. 1. Folliculitis: a purulent inflammation confined to the mouth of the hair follicle, back folliculitis can be caused by Staphylococcus aureus, Malassezia infection. The lesions appear as red follicular papules with pustules in the center of some of them, and are most common on the head, face, neck, chest and back. 2. Acne: Acne is caused by increased androgen secretion, exuberant sebaceous gland secretion, keratinization of follicular sebaceous gland ducts, propagation of Propionibacterium acnes, and immune-inflammatory reactions. It usually appears on the face as well as the chest and back with pimples, nodules and other damages. Back acne, need to clarify the cause of the targeted treatment and medication, you can not just randomly use drugs, so as not to aggravate the condition.