General baby biting nails is not necessarily a lack of what, because the causes of nail biting is more diverse, as follows: 1, due to zinc deficiency or iron deficiency caused by the symptoms, the body lack of zinc, iron deficiency will cause nail biting, and often accompanied by paranoia, picky eaters, etc., this time we need to apply the zinc gluconate oral solution or ferrous succinate to alleviate the 2, due to the nails of the bad habits caused by the nails, if you bite Nail biting, if there is a bad habit of biting nails, over time will cause frequent nail biting, to change the bad habits in time; 3, if there is an itchy finger can also cause nail biting, you can apply Chlorotetracycline to relieve. In summary, the lack of micronutrients is only one of the causes of nail biting, there are other more not due to zinc deficiency, iron deficiency and other causes of nail biting.