Girls’ back acne is usually related to acne, folliculitis and other diseases. 1. Acne: Its causes are mostly related to increased secretion of androgen and sebaceous glands, heredity, blockage of hair follicle openings, and propagation of Propionibacterium acnes, etc. Patients will develop pimples, pustules and other symptoms on the face, chest, back and other places. 2. Folliculitis: The typical symptoms of folliculitis include red papules and pustules, which are often centered on hair follicles and preferably occur on the chest and back. Its cause may be related to Staphylococcus aureus, Malassezia and other germs infections, and can be triggered by excessive sweating, decreased immunity and other factors. There are many reasons that trigger back acne in girls, and patients are advised to seek medical examination to clarify the causes.