There are four physiological reflexes during the neonatal period, one of which is the sucking reflex, which shows that as long as something is put into the mouth, the newborn will make the sucking action. So when the finger is put in the child’s mouth, the child will also behave as a non-stop sucking, which is commonly known as eating hands, which is a physiological phenomenon. However, if you suck your finger for a long time, you will develop a finger-sucking fetish, which is difficult to quit. Parents must not allow their children to develop the habit of finger sucking, as long-term finger sucking can easily cause bacteria in the hands to enter the digestive tract through the mouth and cause digestive tract infections, and can also cause finger dysplasia in serious cases.