Back pimples may be caused by acne, and its causes and triggers include sebum overproduction, proliferation of Propionibacterium acnes, and abnormal keratinization of follicular sebaceous gland ducts. 1. Sebum overproduction: During puberty, sebaceous glands overproduce a large amount of oil due to high levels of androgens, and back acne may be formed when drainage is blocked. 2. Proliferation of Propionibacterium acnes: When the human body is infected with Propionibacterium acnes, it can break down sebum and produce inflammatory factors, causing an inflammatory reaction, which in turn promotes the formation of acne. 3. Abnormal keratinization of follicular sebaceous gland ducts: When the follicle opening is over-keratinized and blocks the ducts, it can affect the discharge of shed epithelial cells and sebum, which can form acne on the back. It is recommended that people with acne on their backs go to a regular hospital in a timely manner to clarify the cause and standardize the treatment under the guidance of the doctor.