Acne on both sides of the back may be caused by acne, Malassezia folliculitis or ringworm, and the site of acne is variable. 1. Acne: often accompanied by enlarged pores and sebum overflow related to heredity, androgen-induced sebum secretion and other factors, can be on the chest and back, shoulders and neck, and other parts of the follicle mouth of the pimples, inflammatory papules, pustules or nodules. 2. Malassezia folliculitis: it is caused by Malassezia follicular inflammatory damage on the back of shoulder, chest, neck and other parts of the hair follicles, the back can form inflammatory follicular papules, papules or pustules, which can extrude the powdery fat-like material, and there can be itching. 3. ringworm: can occur in addition to hair, scalp, nails and palms and toes other than the superficial parts of the skin, lesions at the beginning of the red papules, papules or blisters, can form red patches, the center can have hyperpigmentation. Back persistent acne may also have other reasons, it is recommended to go to the hospital in a timely manner, to clarify the cause of the disease, follow the doctor’s instructions standardized treatment.