Sucking is a natural reflex and infants and young children may suck on thumbs, fingers, pacifiers and other objects. It may help them relax or make them feel safe or happy. Most children stop sucking by age 4. If your child continues to thumb suck that after the permanent teeth have come in, it can cause problems with tooth alignment and your child’s bite. The frequency, duration and intensity of a habit will determine whether or not dental problems may result. Children who rest their thumbs passively in their mouths are less likely to have difficulty than those who vigorously suck their thumbs. If you are worried about your child’s sucking habits, talk to your dentist or consult your child’s pediatrician.