A small piece of hair fell out of the head, considering baldness, may be immune factors, heredity, mental stress, infection and so on. 1. Immune factors: the occurrence of baldness is related to immune factors, the destruction of the immune immunity mechanism of the hair follicle is the key to the occurrence of baldness. 2. Heredity: the occurrence of baldness is also related to heredity, if both parents or one of them has baldness, the chance of children’s disease will increase, and the probability of identical twins suffering from baldness is as high as 55%. 3. Mental stress: long-term mental stress, tension, anxiety, depression, etc. will cause endocrine dysfunction, and hormone levels in the body will also change, affecting the growth of hair and baldness. 4. Infection: If there is herpes zoster, fungal infection, influenza and syphilis and other diseases, it will lead to a decline in the body’s immunity, which will affect the metabolism of the hair, and will also cause baldness. A small piece of hair on the head, it is recommended to go to the hospital for a detailed examination, for the cause of the symptomatic treatment, usually to maintain a positive and optimistic mood, appropriate physical exercise.