Babies are born with sucking motions for milk and hands. Finger sucking begins to appear at 3 to 4 months of age, peaks at 7 to 8 months, and usually subsides after two weeks of age. The emergence of finger sucking is one of the signs that the infant is entering the stage of functional differentiation of the fingers and preparation for hand-eye coordination. As the baby gets older, this action will slowly disappear. However, sometimes infants due to psychological failure to meet the mental tension, fear and anxiety, did not get the full love of parents, and the lack of toys, music, pictures and other visual or auditory stimuli, lonely, then self-sucking finger self-compassion, and then develop the habit of growing up may be inherited, and some even sucked out of the callus. Long-term finger sucking can affect the teeth, gums and jaw development, to the lower jaw protruding, teeth are not aligned, it looks like the upper teeth outward, the lower teeth to the inside, the upper jaw high arch, hindering chewing, while the fingers will also be deformed, and severe may make the nails stop growing. If the baby sucks on the cheeks at the same time, the pressure on the cheeks will be too great, which will also affect the eruption of permanent teeth. If your baby eats his/her hands before 2 years of age, there is no need for special treatment for the time being. If the baby still eats hands after 2 years of age, then parents need to take measures to correct the problem.