There are many reasons why babies eat nails, such as physiological phenomena, bad habits, imitation behavior, malnutrition and so on. 1. Physiological factors: within a week old baby eating nails is a normal physiological phenomenon. 2. Bad habits: for example, baby anxiety, timidity, introversion, insecurity, shock, etc., will also cause the baby to eat nails. 3. Imitation behavior: babies see other people have the phenomenon of eating nails, may imitate other people to eat nails. 4. Malnutrition: anemia, lack of vitamins, lack of trace elements, etc., caused by unbalanced diet and partiality, may also cause babies to eat nails. There may be other reasons for babies to eat nails, should go to the hospital in time to check the cause of the disease, early detection, active treatment.