Babies are born with sucking motions, will eat milk and hands, and have a physical requirement to suck after 3-4 months of age, so you may see your own baby often self-sucking fingers, especially the thumb to settle themselves. This behavior often occurs when hungry and at bedtime, and generally disappears with age at 2-3 years of age. However, sometimes babies are nervous, fearful and anxious because they are not psychologically satisfied, they are not sufficiently loved by their parents, and they lack visual or auditory stimulation such as toys, music, pictures, etc. When they are lonely, they suck their fingers for self-soothing, and this becomes a habit, and when they grow up, they may continue to do so, and some of them even suck out their calluses. Long-term finger-sucking can affect the development of teeth, gums and jaws, causing the jaws to protrude, the teeth to be uneven, and the upper teeth to look outward, the lower teeth to look inward, and the upper jaw to be high and arched, preventing chewing, while the fingers can also be deformed, and in serious cases, the nails may stop growing. If the baby also sucks on the cheeks, the pressure on the cheeks is too high and it will affect the eruption of permanent teeth. Therefore, it is better for parents to adjust the finger sucking when the child is small, especially in infancy, and to give more care and caress to the baby on a daily basis, talk and play games with the baby, so as not to make the child’s world too boring, too helpless and too helpless.