The acne on the back of the chest is mostly considered to be caused by folliculitis, acne, etc. The acne on the back of the chest is mostly considered to be caused by folliculitis. 1. Folliculitis: acne on the back of the chest may be folliculitis, folliculitis is usually caused by bacterial or fungal infections, commonly caused by Staphylococcus aureus, Malassezia, etc., manifested as red papules and pimples centered on hair follicles, accompanied by local itching and pain. 2. Acne: Increased secretion of androgens after puberty, increased sebaceous gland secretion, and propagation of Propionibacterium acnes may induce acne, resulting in chest and back acne. If you have acne on your chest and back, you should go to the hospital in time to find out the cause and get standardized treatment.