Is my child’s nail biting a nutritional deficiency? Xiaoyu’s father came to the office and asked me to look at the child’s trace element report. I told him that calcium, iron and zinc were all within the normal range, and the lead indicator was not high. Xiaoyu’s father looked at me with astonishment: “All normal? Then why is my Xiaoyu biting his nails?” In his opinion, Xiaoyu often bites his nails because he is deficient in some trace elements or has lead poisoning, but the test report was normal. I asked him to bring the child to the clinic for a look. The next day, a slightly chubby Xiaoyu came in, shy under the parents’ narrative, with ten short and uneven nails on his outstretched hands. In fact, in addition to nail biting, Xiaoyu was also a glutton for punishment. I suggested that Xiaoyu take a psychological test. The psychological test suggested that Xiaoyu in second grade had normal intelligence, but had poor motor coordination and difficulty with writing, as well as low self-awareness and negative anxiety. Because of his study skills problems, he was often criticized by his teacher for his slow homework and poor handwriting, and his parents chastised him for accompanying him for long hours to do homework. Xiaoyu was also anxious and nervous about not doing well on his own and unknowingly chewed his fingernails to relieve his emotions. The parents saw the child biting his nails and reprimanded and punished him, reinforcing Xiaoyu’s behavior and becoming a vicious cycle that has not improved in over a year. In fact, there are many families like Xiaoyu’s. According to statistics, among children aged 6-12, the prevalence of “frequent” and “almost all-day” finger-sucking is 12 percent. The prevalence of fingernail biting is 44%. Among 14-year-olds, nail biting was present to varying degrees in 55% of children. As we all know, sucking is a primitive reflex, and any object that touches the baby’s mouth and lips will cause a sucking reflex, and in infancy, it is common to suck one’s own fingertips, and this phenomenon generally decreases after 2-3 years of age. However, in times of loneliness, anxiety, and physical discomfort, finger sucking can be used to masturbate, reduce anxiety, and divert attention, and thus finger sucking may still occur. If these behaviors occur occasionally or do not last long, they should not be considered pathological. As children grow older and have more contact with the outside world, this bad habit can usually be eliminated unknowingly. However, if bad situations are frequent, finger-sucking behavior may become a fetish that is difficult to eliminate. As for the reasons for nail biting, like finger sucking, it usually occurs when the child is emotionally stressed or depressed and is often accompanied by sleep disturbances, grinding of teeth, and finger sucking. Thus, it seems that fingernail biting in children is not necessarily a problem of trace elements in the body, but more of a psychological-behavioral problem. Parents should actively look for factors that cause tension and apprehension, and promptly improve the children’s living environment and develop healthy habits. Xiaoyu later participated in special training in learning skills and sensory integration therapy, balance function training, improved coordination and writing skills, and better speed and quality of doing homework. At the same time, the parents changed the way they used to spend time with their child, focusing on encouragement and help, and insisted on giving Xiaoyu daily nail care to reduce negative stimulation. Six months later, Xiaoyu’s nail biting habit disappeared without her knowing it. Of course, the cause of nail biting behavior is not necessarily the same for every child, so if your child is also biting nails, please find out the cause and prescribe the right medicine.