Hair loss refers to the phenomenon of hair loss caused by various reasons, mainly including physiological hair loss and pathological hair loss. 1. Physiological alopecia: Hair has its own growth cycle, including the growth period, regression period and resting period. Hair grows to a certain extent, can be physiological shedding, hair loss of about 50 ~ 100 per day. After that, it can grow out gradually and generally does not need special treatment. 2. Pathological alopecia: Pathological factors may also lead to hair loss, such as congenital alopecia, dysplasia, abnormalities in the hair shaft structure, fungal and bacterial infections, hypothyroidism, androgenetic alopecia, baldness caused by alopecia areata, and so on. Skin diseases such as lichen planus, discoid lupus erythematosus, exfoliative dermatitis, and limited scleroderma can also cause hair loss. In addition to these, scarring alopecia, plucking ringworm, hair loss caused by antitumor drugs, anemia, malnutrition, cirrhosis, syphilis, meningitis and other causes of hair loss. To summarize, there are more causes of hair loss. If it is physiological hair loss, usually no medication is needed. If you suspect that it is caused by pathological factors, it is recommended that you go to the hospital in time for consultation and standardized treatment under the guidance of the doctor after a clear diagnosis.