Thumb sucking is a normal and acceptable behavior in babies and toddlers. In fact, about 75 percent of babies under a year old suck their fingers or thumb. Sucking a thumb helps them feel secure and happy and helps soothe a child who is separated from their parents or is otherwise under stress. Sucking the thumb is also relaxing and can help a child go to sleep.
When Does Thumb-sucking Become a Problem?
According to the American Dental Association (ADA), most children stop sucking their thumb when they are between two and four years old. Children this age are spending more time exploring the outside world. They are also spending more time with other children, and their peers will tease them or refuse to play with them if they continue sucking their thumb when they reach school age.
Sucking the thumb becomes a problem if the child continues to do it past the age of five. Prolonged sucking of the thumb can affect the growth and development of the mouth, particularly the palate.
A small child’s bones are extremely soft and pliable, and the palate can become abnormally narrow as it shapes itself around the thumb. An abnormally narrow palate can lead to problems with the developing teeth like crowding or malocclusions (“bad bites”) as there is too little room in the child’s jaws to properly accommodate them.
Prolonged sucking can also affect the alignment of the teeth. It can cause such malocclusions as an open bite in which the front teeth don’t touch when the mouth is closed. Generally speaking, an older child who continues to suck their thumb may develop protruding or slanting teeth.
The problems are particularly likely to be severe in children who vigorously suck their thumb as opposed to those who let their thumb sit passively in their mouths.
Parents will hear popping sounds as the child sucks their thumb if they do so aggressively. In addition to the aforementioned problems, aggressive sucking can cause the child to develop sore or ulcers in their mouth. The child may also develop chapped skin, fingernail infections, or calluses.