Back acne is also known as common acne, caused by the following reasons: First, genetic factors, some patients have a family history. Second, androgen secretion, after puberty androgen secretion, resulting in sebaceous gland function activity, increased secretion of oil, sebaceous gland duct keratinization, the formation of acne in the back. Third, bacterial infection, the back of a large number of propionibacterium acnes reproduction, causing inflammatory papules, nodules, cysts and so on. Fourth, drug-induced, long-term oral corticosteroids and iodide caused. Fifth, other factors, such as often stay up late, eat high sugar and high fat food and too much chili.