Ketoconazole lotion has no therapeutic effect when the back acne is acne. Ketoconazole lotion may be used if the back acne is caused by Malassezia folliculitis. Acne is often referred to as acne vulgaris, and back acne may be related to androgen levels, Propionibacterium acnes colonization, etc., rather than a fungal infection, making ketoconazole lotion ineffective for it. Malassezia folliculitis can also result in multiple red papules and pimples on the chest and back, similar to acne, and the etiology is related to the colonization of Malassezia. Treatment can use ketoconazole lotion, which has antifungal and anti-inflammatory effects. Acne on the back need to go to the hospital in time, clear diagnosis and follow the doctor’s prescription medication.