Acne all over the back i.e. pimples all over the back may be caused by acne, contact dermatitis, herpes, etc. 1. Acne: It may be caused by abnormal secretion of androgen, clogged pores, infection, etc. It may appear as whiteheads, blackheads, pimples and other symptoms. When acne occurs on the back, it can also appear that the back is full of pimples. 2. Contact dermatitis: refers to the inflammatory reaction of the skin at the contact site or even outside the contact site after the skin comes into contact with certain exogenous substances. In acute attacks, erythema, edema, accompanied by papules, blisters and other symptoms. 3. Herpes: manifested as a limited, fluid-containing, cavernous damage above the skin surface, mainly caused by human herpesvirus infection, a class of skin diseases. Viral infection of the skin on the back may cause herpes simplex, herpes zoster and other diseases, thus causing the above symptoms. In addition, it is recommended that patients with acne on their backs go to the hospital in time and follow the doctor’s instructions for treatment to avoid delaying the condition.