Children love to gnaw fingernails, may belong to the normal physiological behavior, pathological conditions such as nail biting fetish or micronutrient deficiencies in the body can also have gnawing fingernails performance. 1. Physiological behavior: 3 to 4 months of infants in the physiological need to suck, can be masturbated by sucking fingers, mostly at bedtime or when hungry, with the age of the gradual disappearance. 2. Nail biting fetish: an undesirable psychological disease arising from unsatisfied emotional needs or emotional tension, mostly seen in preschool or school-age children, parents are advised to distract the children’s attention to other things in time and show more care and love to the children. 3. Trace elements lack: such as children lack of zinc in the body, can affect the digestive function, there is a lack of appetite, anorexia or xenophagia, at this time will often gnaw fingernails. Found that the child is good at nibbling nails, to take the child to the hospital in a timely manner, in accordance with the doctor’s instructions for treatment at the same time, the parents to be cared for and guidance, to help the child to overcome the bad habits.