There are many causes of acne on the chest and back, mainly acne and folliculitis. 1. Acne: There are also many reasons why acne causes acne on the chest and back, such as mental immune factors, improper diet, and Propionibacterium acnes infection. (1) Psycho-immune factors: High mental stress, prolonged late nights, anxiety, irritability, etc., can lead to a decline in immunity, and therefore may lead to acne on the chest and back. (2) Improper diet: daily like to eat heavy food, such as spicy, fried, spicy food, etc., will stimulate the chest and back sebaceous gland secretion, thus leading to acne. (3) Propionibacterium acnes infection: Localized skin infections with Propionibacterium acnes allow it to grow and multiply in the local skin, which can cause acne. 2. Folliculitis: Folliculitis may be related to bacterial and fungal infections and poor skin cleansing, which can also lead to acne on the chest and back. (1) Bacterial and fungal infections: localized hair follicles suffer from bacterial infections, such as Staphylococcus aureus, and Malassezia infections also lead to inflammatory episodes, which can manifest as acne on the chest and back. (2) daily skin cleaning is not in place: usually do not like to take a shower, especially the back of the skin is not easy to clean in place, resulting in the accumulation of cell metabolism products hair follicle location, in the long run will cause the chest and back always long acne. Caused by the back of the chest is always long acne for many reasons, after the symptoms suggest that patients go to the hospital in a timely manner to improve the examination, under the guidance of the doctor to take standardized treatment, do not private treatment, so as not to lead to adverse consequences.