Nail biting in children is related to imitation of others, anorexia, and obsessive-compulsive disorder (OCD). 1. Imitation of others: For children who have not had the habit of biting their nails in the past, they may always bite their nails because they imitate the nail-biting behavior of other people around them. 2. Ectophagia: The etiology of ectophagia is still unclear, and may be related to nutritional deficiency, mental and psychological factors, and family education background. The common manifestation of heterophilia is that children often eat non-nutritive, non-food items, such as dirt, hair, intellectual disabilities, etc., and may also be manifested as always biting their nails. 3. Obsessive-Compulsive Disorder (OCD): OCD is related to genetic factors, personality traits, psychological environment, etc. Some children may develop overeating behavior due to OCD, which may be manifested as always biting nails. For some children, the compulsive behavior of always biting nails can occur due to uneven nails, prompting the edges of the nails to be neat. In addition to the above, bad habits, unmet emotional needs, emotional stress and other conditions can also cause children to bite their nails all the time. It is recommended to go to the hospital in time, complete the examination to clarify the cause of the disease, and then give targeted treatment or therapy under the guidance of the doctor.