A dark and shiny hair is not only a symbol of health but also a sign of perfect image. Hair health has become a growing concern for people. Due to the increase in work pressure and lifestyle changes, hair diseases have increased, like a cruel killer, invading quietly and ruthlessly taking away our health and charm. Therefore, it has become a difficult task for dermatologists to study the causes and treatment of hair diseases and to solve the problems of hair loss of patients. Why do people lose their hair? 1, androgenetic alopecia: also known as androgenetic alopecia, male pattern hair loss, 95% of male patients. Research found that the free testosterone and dihydrotestosterone in the serum of patients with alopecia are higher than normal people, and its etiology and pathogenesis are mainly related to three substances: (1) androgens: high androgens, resulting in accelerated rate of matrix mitosis, differentiation time is not enough to make the hair daisy; increase the amount of resting hair per unit of time; make the hair density and diameter progressive decline, the final hair follicles into Cui hair follicles, that is, the clinical baldness. (2) AR expression: androgen receptor, the expression of AR in the alopecia area of AGA patients was higher than that in their own non-alopecia scalp as well as in the allogeneic normal scalp, indicating that there is a correlation between the high value of AR in each skin structure and the thinning degree of hair follicles in the balding area; (3) metabolic enzyme 5α-reductase::5α-reductase activity was 3-8 times higher in the anagen phase of hair follicles than in the resting phase, and the 5α-reductase level in the scalp hair follicles of AGA patients was The level of 5α-reductase in scalp hair follicles of AGA patients is significantly higher than that of normal people, which increases the concentration of DHT in the scalp, and DHT binds to the corresponding receptors at the hair follicle site, which affects the hair follicle cycle, causing the initial phase of hair growth to be significantly shorter and the hair follicles to gradually shrink, thus leading to the transformation of local hair on the scalp from terminal hair to fine hair until shedding and eventually causing baldness. Genetic factors have shown that the prevalence of AGA in men whose parents or grandparents have baldness is about 2 or 5 times higher than the prevalence in men without a family history of baldness, proving that genetic susceptibility is an important factor in the development of AGA, and it has been reported that more than 70% of AGA patients have a family history of genetic predisposition. Scalp blood supply Scalp subcutaneous blood flow studies show that subcutaneous blood flow in normal people is 10 times more than subcutaneous blood flow in other parts of the scalp, while blood flow in balding areas of AGA patients is 2 or 6 times less than that of normal people. 2, baldness The cause of baldness is not yet clear, but it may be related to mental stimulation, excessive stress, physical exertion, autoimmune defects, and genetic factors. Mental factors include personal factors, family factors and social factors. Patients who are under long-term mental stress due to examinations, family disputes and work account for the majority of cases. Immune factors are considered to be the main factor in the occurrence of baldness, and it is common for patients with baldness to have autoimmune diseases such as diffuse goiter, hypoadrenalism, diabetes mellitus, autoimmune hemolytic anemia, etc. A large number of experiments have shown that the proportion of patients with a positive family history is 10-42%, so we can see the importance of genetic factors in the development of baldness. 3. Resting hair loss Fever, anesthesia, surgery, shock, malnutrition, overeating, blood loss, prolonged and difficult labor, immune diseases such as lupus erythematosus, and severe mental factors stimulate the hair follicles to enter the resting phase early from the anagen phase, and the normal terminal hair is lost. Drugs such as warfarin, heparin, indomethacin, gentamicin and other drugs can cause resting hair loss. Oral contraceptives are an important cause of resting hair loss. Postpartum alopecia is a physiological extra-long hair loss phenomenon that occurs within six months after birth. 4, long-term hair loss hair in the growth phase is very sensitive to many chemical factors, high doses of X-rays, anti-metabolic drugs, cytotoxic drugs, thallium, selenium cysteine, heavy metals, vitamin A overdose 5, hair pulling fetish is a common bad habit in children, manifested as children consciously or unconsciously, uncontrollable pulling out their own hair, manifested as multiple hair thinning, generally not accompanied by other psychiatric symptoms, intelligence Normal, occasionally anxiety, depression and other adverse emotions.