1, androgens: elevated or sebaceous gland affinity for androgens or enhanced 5a reductase activity; dehydroepiandrosterone (DHEA) secreted by adrenal glands and testes and testosterone (T) become dioxytestosterone (DHT) under the action of 5a reductase, which binds to androgen receptors in sebaceous gland cell plasma and promotes sebaceous gland cell proliferation and sebum overflow rate (SER). 2, abnormal keratinization of follicular sebaceous gland ducts: the formation of acne is related to the lack of local VitA and linoleic acid. Pan Hu, Department of Dermatology and Venereology, PLA 102 Hospital 3, microbial action: Acinetobacter acnes (P. acne), Staphylococcus epidermidis and Sporothrix furfur in the hair follicle sebaceous gland decompose triglycerides in sebum, producing free fatty acids and some enzymes released by these microorganisms, causing inflammation around the hair follicle. 4, inflammatory reaction; inflammatory mediators such as neutrophil chemokines and some enzymes released cause inflammatory reaction and subsequent destruction of hair follicle wall. Zinc and linoleic acid can affect inflammation through their effect on PMNS. 5, genetic factors: affect androgen secretion, degree of inflammatory response (clinical type, damage distribution and pathology) and follicular keratinization process. 6, psychosomatic factors: affect the degree of inflammatory response. Pathology: hyperkeratosis and thickening of the upper part of the follicular sebaceous ducts (hair funnel); acne containing keratinized cells, lipid droplets and some microorganisms; inflammatory reaction around the hair follicles and capillaries. Clinical manifestations Age of onset: 12-14 years; exacerbation: 15-17 years for women and 17-19 years for men; remission: 25-30 years, but also around 40 years. Rash type: acne (whiteheads, blackheads), papules, pustules, nodules, cysts and scars (icepick-like, atrophic, hypertrophic). Grading (degree): mild, moderate and severe, Cunliff proposed 0-10 classification method, 0-2 grade every 0.25 as a boundary, later 3-10 grade, based on the depth of damage, type, number and distribution site, cumbersome and not easy to grasp. In China, the Samuelson 9-degree classification method modified by Tie-Feng Wu is now used for grading the disease;