Generally, children give up mouth-related behaviors automatically before they are 3 years old. For example, sucking thumb, sucking fist, containing fake nipple, etc. At this time, if the sucking instinct is not satisfied from the diet (such as feeding), it will be satisfied from other places (such as sucking the thumb with fake nipples, etc.). 1, seeking excitement. Biting your nails hurts a little, but it's not serious. Get a pleasure when biting. 2, life is sometimes monotonous, I feel lonely, my hands are always on my body, it is very convenient to play, and I have bitten my nails on my fingers before, so I still bite when I have nothing to do. 3. Mother's way of beating and cursing actually strengthened his habit. Beating and cursing are fierce, and he is psychologically unbalanced, so he has to find his own way out and get comfort from biting his nails. 4, autistic children will bite their nails, lack of parental love will bite their nails, and they will not bite their nails when they are beaten. Your child's situation may fall into the last category. It would be much better if he was seen biting his nails instead of beating and cursing. 5, zinc deficiency: children's zinc deficiency performance: loss of appetite, eclipse, do not like to eat normal food, do not eat leeks, like to eat some non-food and other partial eclipse habits. Zinc deficiency can also lead to children's hyperactivity, inattention, white spots on nails, biting fingernails, acne, frequent abdominal pain, slow growth of height, decreased digestive function, decreased immune function and increased chances of infection. Many studies show that the zinc content in children with mental retardation, poor memory and poor academic performance is also lower than normal. The doctor said that people's hands have the most contact with the outside world, especially children, and there are a lot of pathogenic microorganisms such as bacteria and viruses in the fingernails and fingertips. When children bite their nails, they will undoubtedly unconsciously bring a lot of germs into their mouths and bodies, leading to oral or dental infections, and even serious digestive tract infectious diseases such as bacillary dysentery or intestinal parasitic diseases such as ascariasis and pinworm disease. Often biting nails can also cause harm to children's teeth, resulting in irregular tooth arrangement, such as tooth exposure and missing front teeth, which affects children's appearance. Nail biting may also cause nail deformity, destroy nail bed, cause bleeding or infection, damage the deck, shorten the deck, make the periphery irregular, make the deck surface rough and lose its original luster. If it invades nail groove, it may cause paronychia. For children who bite their nails, you can try the following methods: 1, take your child to the mental health clinic for consultation. Children believe the doctor's words more.