1.psychogenic alopecia Psychogenic alopecia is hair loss caused by excessive mental stress. When mental stress is excessive, the scalp trichomes contract and the capillaries that carry nutrients to the hair follicles contract, causing local blood circulation disorders, resulting in ecological changes and malnutrition of the hair. Mental stress can also cause excessive sweating and sebaceous gland secretion, producing head scale and reducing the quality of the environment in which hair lives, which can lead to hair loss. Psychogenic alopecia is a temporary hair loss, after improving the mental condition and reducing mental stress, generally can be self-healing. 2, androgenic alopecia, also known as early baldness, commonly known as “shedding”. The reason for this is related to genetics and androgens, and it is permanent hair loss. It is characterized by progressive hair loss on the forehead and top of the head, mostly seen in men who are engaged in mental work, and hair loss often starts to appear around the age of 20-30. The hair loss usually starts from the forehead and both sides of the temporal area, with the front hairline gradually receding and the forehead becoming higher. As age increases, the hair on the top of the head gradually thins out and even exposes the scalp, while there is still hair in the back of the occipital area and the hairline on both sides. The course of androgenetic alopecia progresses slowly, and female patients have a lighter degree of hair loss, with most of them having thinning hair on top and thin and soft hair. Seborrheic alopecia is a type of hair loss that occurs on the basis of excessive seborrhea, often accompanied by increased dandruff, oily scalp, and obvious pain and itch. The hair is fine and soft, some of them are accompanied by seborrheic dermatitis of the scalp, and the hair loss starts gradually from the top of the head and spreads to the forehead. The scalp is oily and bright red, with yellow oily scabs. The treatment of seborrheic alopecia must first pay attention to the health care of the hair, eat less greasy and spicy food, diligently wash the hair, use local medicine to remove grease, reduce dander, anti-inflammatory and anti-itch. 4.Patch baldness, commonly known as “ghost shaving”, is a kind of localized patchy hair loss, with sudden onset and slow onset. The cause is related to the temporary inhibition of hair growth caused by neuropsychological factors, endocrine disorders and immune dysfunction. It is characterized by the sudden appearance of round or oval patchy hair loss on the head, mostly without conscious symptoms, smooth and shiny scalp at the affected area, and when the disease progresses, the damage expands and the peripheral hairs are loose and easy to be lost, individual patients can lose all their hair, and in severe cases, eyebrows, beard, axillary hair and pubic hair can also be lost. The disease can be self-healing, but often relapses, and the course of the disease can last for several months or longer. During the recovery period, the new hair is thin, soft, grayish white, gradually coarse and black, and finally returns to normal. For the treatment of alopecia areata, the cause should be searched for, and then psychological treatment such as psychological guidance should be used, which can also be supplemented by internal and external medication. 5.Physical alopecia Including mechanical alopecia, burn alopecia and radioactive damage alopecia. Mechanical baldness is the breakage or loss of hair caused by certain special hairstyles, such as braids, buns and other hair styles for women, and split hair styles for men. Hair needs to be kept somewhat naturally loose and properly elastic to pressure. If it is directly subjected to tension and tied up tightly with ribbons or rubber bands, it will easily cause the forehead hair to break and fall out and the hairline to recede. Excessive exposure to ultraviolet light from sunlight and frequent use of hot blow dryers also tend to thin the hair. Radiation damage is clinically divided into four degrees, all of which can cause hair loss. 6, chemical hair loss Tumor patients receiving anti-cancer drug treatment, long-term use of certain chemical agents such as commonly used gentamicin, allopurinol, methylphenidate, thiouracil, trimethoprim, propranolol (insulin), phenytoin sodium, aspirin, anti-inflammatory pain, birth control pills, etc. often cause hair loss. Hair cosmetics such as perms, hair cleansers and hair dyes are also common causes of hair loss. In recent years, the incidence of women’s hair thinning has been increasing, which may be related to the abuse of hair cleansers due to some irresponsible advertising. 7, symptomatic hair loss Anemia, liver and kidney disease, malnutrition, systemic lupus erythematosus, dry syndrome, acanthosis nigricans, and febrile diseases such as enteric typhoid, pneumonia, meningitis, influenza, etc. can often lead to hair loss, resulting in thinning hair, this kind of hair loss is called symptomatic hair loss. 8, nutritional metabolic alopecia Excessive sugar or salt consumption, protein deficiency, iron deficiency, zinc deficiency, excessive selenium, etc., as well as certain metabolic diseases such as argininosuccinic aciduria, homocystinuria, hereditary orothenic aciduria, methionine metabolism disorders, etc., are also causes of hair loss. 9, infectious alopecia Hair loss caused by fungal infection, parasites, viruses and septic skin diseases is called infectious alopecia. Head chickenpox, herpes zoster virus, human immunodeficiency virus (HIV), Mycobacterium leprae, Mycobacterium tuberculosis, syphilis pale spirochetes, and various fungus-induced tinea capitis can cause hair loss; local skin lesions such as seborrheic dermatitis, lichen planus, infection with mold or parasites can also cause hair loss. 10, endocrine disorder alopecia The hair loss caused by hormonal imbalance in the body due to abnormal function of the endocrine glands is called endocrine disorder alopecia. Postpartum, menopause, oral contraceptives, etc. can cause estrogen deficiency and hair loss within a certain period of time; hypothyroidism or hyperthyroidism, hypopituitarism, hypoparathyroidism, adrenal tumors, advanced acromegaly, etc., can lead to hair loss. The phenomenon of hair loss should not be underestimated. Once the phenomenon of hair loss occurs, you should promptly choose a regular hospital for treatment.