Acne on the back during puberty may be caused by acne, folliculitis and other diseases. 1. Acne: Acne may be caused by factors such as increased androgen levels, Propionibacterium acnes infection and abnormal keratinization of sebaceous glands. Patients will have pimples, comedones, and pustules on the skin, and they are usually found on the head, face, chest, and back. 2. Folliculitis: the onset of folliculitis is mostly related to bacterial infection. Factors such as excessive sweating, hair pulling and trauma may also trigger the disease. Clinically, red papules and pustules are the typical symptoms, which are commonly found on the head, face, chest and back where hair follicles are abundant and secretion function is vigorous. The causes of adolescent back acne are not one, and patients are advised to go to regular hospitals for relevant examinations to clarify the causes.