There is no best way for a 14 year old child to change his nail biting. Nail biting may be gray nails, mental problems, zinc deficiency, etc., and should be treated symptomatically for the cause of the disease. 1. gray nails: dermatophytes invade the nail plate or nail bed will lead to nail thickening, thickening, brittleness or shedding, buckling, some patients will unconsciously bite their nails, picking their nails, this situation needs to be treated for gray nails, you need to apply topical amorphophallus powder, and at the same time, according to the course of oral itraconazole, terbinafine. 2. Mental problems: long-term learning pressure or mental tension, should be adjusted from life, distraction, you can do some other things of interest, the symptoms of the heavier recommended to go to the hospital for psychological counseling. 3. Zinc deficiency: If you usually have the habit of picky eating, it is easy to appear zinc deficiency, zinc deficiency patients may have heterophilia nail biting, it should be treated by zinc supplementation, you can choose zinc gluconate, zinc sulfate, zinc acetate and so on. If the symptoms of nail biting are not relieved, or accompanied by other symptoms, you should go to the hospital in a timely manner, and give targeted treatment after clarifying the cause.