Acne on the back of the chest may be related to Malassezia folliculitis, acne and other diseases. 1. Malassezia folliculitis: an inflammatory disease of the hair follicle and its surrounding tissues caused by the overgrowth of Malassezia bacteria inside the hair follicle. It is most common on the chest, back and shoulders and neck, where sebaceous glands are more abundant. It is characterized by scattered, hemispherical papules, accompanied by itching, and in severe cases, pustules may appear, and the itching symptoms will be aggravated when sweating. 2. Acne: It may be related to excessive secretion of sebaceous glands, abnormal levels of androgens, and abnormal keratinization of cells around hair follicles, etc. It is a chronic inflammatory disease, which occurs in adolescent men and women, and the symptoms will gradually decrease after puberty. It occurs on the face, back, chest and other parts of the body, and is clinically characterized by the appearance of pimples, papules, nodules, cysts and so on. Acne on the back of the chest may also be other diseases, such as contact dermatitis, eczema, etc., and need to be treated with topical glucocorticoids, oral antihistamine drugs. It is recommended that patients with acne on the back of the chest go to a regular hospital in a timely manner, to clarify the diagnosis and cooperate with the doctor’s treatment.