1, congenital factors: some congenital factors such as developmental defects, various syndromes, premature aging disease, etc. can cause complete absence or thinning of hair; congenital hair follicle dysplasia can cause hair thinning and breaking; congenital baldness is an autosomal dominant genetic disease, mostly seen in the offspring of consanguineous marriages. 2, mental factors: excessive mental stress is a common cause of hair loss. Mental tension, depression, fear or serious insomnia can cause neurological disorders, resulting in capillary constriction, and the hair follicles do not get enough blood supply, so the hair is easy to fall out, most of the common clinical baldness and total baldness belong to this situation. 3, disease factors: anemia, malnutrition, acute hyperthermia, infectious diseases or long-term liver disease, if the interference with the function of hair root hair mother cells, it will affect the growth and color of hair, or even make the normal division of hair mother cells is inhibited, and the hair is in a long-term resting period, and therefore hair loss. 4, the relationship between drugs and hair: many drugs can damage hair, the most common is the treatment of cancer chemotherapy drugs, many people know that chemotherapy can cause hair loss, this is because chemotherapy drugs can not only kill cancer cells, but also kill any rapidly dividing cells other than cancer cells, including the hair root cells in the growth phase, so there will be about 90% of the hair loss, usually when chemotherapy stops hair will gradually grow again. 5, genetic and endocrine factors: common clinical seborrheic alopecia is not only related to family genetic factors, but also has a close relationship with androgen metabolism, in the scalp of patients with seborrheic alopecia, the level of a substance called dihydrotestosterone will increase, this substance will destroy the hair growth cycle, that is, shorten the time of hair growth period, accelerate the resting hair loss, so that the number of hair loss per day exceeds In the long run, more hair is shed and less hair is grown, which eventually leads to hair loss. In addition, insufficient estrogen levels, hypopituitarism, thyroid dysfunction, adrenal tumors and other factors, can lead to hair loss. 6, the relationship between nutrients and hair: protein, multivitamins and trace elements are closely related to the growth of hair, so malnutrition due to dieting and weight loss, partiality and other reasons, as well as unbalanced nutrition or absorption disorders due to poor digestion, chronic wasting diseases, can lead to the normal growth of hair is inhibited and enter the resting phase, hair thinning, scorching, premature graying or loss. Remind hair loss patients, regardless of the cause of hair loss, during the treatment, must ensure adequate nutrition supply to achieve the purpose of treatment. 7, physical and chemical factors and hair: physical factors such as strains, abrasions, burns and electrical injuries can cause hair loss; excessive exposure to ultraviolet rays in the sun and frequent use of hot blow dryers can cause damage to the hair, and over time the hair is prone to thinning. Chemical factors such as shampoo, perm, hair dye, hair styling agent and other hair cosmetics are also common causes of hair loss. Therefore, be sure to use qualified and high quality hair cleansing products, minimize hair coloring and perming, do not use mousse hair gel type hair styling agent, rinse clean after shampooing, do not leave the residue of shampoo products in the hair.