Nail gnawing may be a normal phenomenon due to the child’s need to suck, or it may be due to xenophobia, or it may be due to nail biting fetish. 1. Physiological factors: it is a normal phenomenon for children within 1 year of age to have the need to suck, and this phenomenon will usually subside later, so it may be normal for children of this age to gnaw their nails. 2. Ectophagia: Ectophagia is a disease caused by nutritional deficiency, mental and psychological factors, which can also lead to the phenomenon of nibbling nails in children, and children can also appear to eat paper, hair, soil and other symptoms. 3. Nail biting fetish: nail biting fetish is a kind of disease related to mental tension, heredity and other factors, the disease can also lead to children appear to gnaw the phenomenon of nails, in addition, the child was bitten by the nails can also appear under the nail hemorrhage, inguinal inflammation and other manifestations. After eliminating physiological factors, if the child’s nail biting symptoms continue to be unrelieved, it is recommended to consult a doctor in time to identify the cause and ask the doctor to deal with it.