Blackheads on the back, a type of acne, are related to genetic factors, androgen-induced mass secretion of sebaceous glands, hyperkeratosis of follicular ducts, and propagation of Propionibacterium acnes. Increased sebum causes conical pimples to appear on hair follicles, secretions cannot be easily discharged, and sebum plugs are oxidized, resulting in the formation of blackheads and pimples. 1. Genetic factors: Acne is directly related to genetic factors. 2. Androgen-induced massive secretion of sebaceous glands: androgen stimulation promotes the secretion of sebaceous glands in hair follicles and the increase of oily secretions. 3. Hyperkeratosis of follicular ducts: Stimulation of secretions can cause hyperkeratosis of follicular ducts inducing acne. 4. Propionibacterium follicularis reproduction: Microorganisms such as Propionibacterium acnes grow and reproduce, forming an inflammatory reaction, which can also lead to blackheads and pimples. There may be other reasons for blackheads on the back, so it is recommended to go to the hospital for examination and active treatment.