Hair loss may be a normal phenomenon, baldness, seborrheic alopecia and systemic diseases. 1. Normal phenomenon: If the number of hair loss is relatively small, not more than 100 per day, it is usually a normal physiological phenomenon, which is related to the metabolism of hair. 2. Patchy baldness: Patchy baldness is usually related to genetic factors, autoimmune factors, mental factors, etc. The main symptom is patchy hair loss. 3. Seborrheic alopecia: androgenetic alopecia, related to heredity and androgen. It is characterized by progressive reduction and thinning of hair on the head, and hair thinning. 4. Systemic diseases: if the patient is malnourished or has severe anemia, there may also be hair loss, in addition, malignant tumors in the late stage of chemotherapy is also prone to hair loss. If the hair loss is more serious, it is recommended to actively go to a professional hospital for relevant examinations, a clear diagnosis, and actively follow the doctor’s instructions for treatment.