Endocrine dysfunction, increased or relatively high secretion of androgens → sebaceous glands secrete a lot → excessive oil → keratin layer proliferation, pore enlargement, blockage → keratin layer bulge, oil blockage of pores → Propionibacterium acnes proliferates in the absence of oxygen → leads to infiltration of inflammatory cells → formation of pustules and nodules → follicle wall rupture → follicle inflammation → acne formation