Children often bite their fingernails is also a relatively common phenomenon, and there are many reasons for this phenomenon. For example, habitual behavior, micronutrient deficiencies, parasitic infections in the body, mental stress and other reasons caused by a variety of reasons. From a medical point of view, the nail biting behavior of children is also called nail biting disorder, the symptoms are repeated nail biting, is also a common bad habit in childhood, both boys and girls will appear, but most of the children as they grow older nail biting bad behavior will also change on their own. Micronutrient deficiencies are also the main cause of finger biting in children, such as a lack of calcium, magnesium and other trace elements in the body can lead to this behavior. Parasitic infections, such as roundworms and pinworms, can also cause children to bite their fingernails. In addition, children’s fingernail biting behavior and nervousness also have a certain relationship, such as children into the nursery, the school will easily appear nervousness, thus appearing to bite nails, especially some introverted, sensitive, anxious and other personality characteristics of children, more likely to appear this behavior. Nail biting can have an impact on a child’s health, so parents need to correct it in a timely manner, and need to do micronutrient and stool tests to rule out that it is caused by these two factors.