Many young children suck their thumbs as a way of self-soothing or to help them fall asleep. For older children it becomes a coping mechanism to deal with any worries or to relieve boredom. This habit is natural and healthy. So the key is just be patient with your child as they will eventually grow out of it as they learn other ways to cope physically, mentally and emotionally in different situations or new routines.
As a dentist, our immediate concern is only if your child is habitually still sucking by age 4-6 as that is when their permanent teeth starts to come through. Notice if your child is intensely sucking or just resting their thumb in their mouth. Intense thumb sucking can cause teeth to be misaligned. Vigorous, prolonged sucking can alter the palate, affecting the child’s bite and speech development.
As a parent you probably would like them to kick the habit sooner than later. So our best advice is to always offer positive encouragement and visit your child’s dentist early if you feel that they are starting to develop dental or speech problems.