Thumb sucking is a common practice among infants and young children as a self-soothing technique. It usually involves sticking the thumb inside their mouths but some may use other fingers or the whole fist. Many children find this act to be soothing or entertaining, particularly during the first few months or years of life.

Ultrasound images have shown some babies sucking their thumbs in the uterus. Throughout infancy and the toddler years, thumb-sucking is quite common. It tends to peak around age 2, and most children no longer engage in this habit by 4 years of age. In most cases, thumb-sucking is harmless. However, the practice can cause problems in children who continue to suck their thumbs for long periods of time.

Parents should be concerned if they notice changes in the shape of the child’s mouth or teeth. Other symptoms associated with problem thumb-sucking include chapped lips, cracked skin, calluses and fingernail infections.

Thumb-sucking can become a problem when it continues past the age of 4 years, especially after permanent teeth come in around age 6. Children who continue to suck their thumbs after this point have the potential to develop dental problems if they suck too hard or press on their palate (roof of the mouth) or teeth.

Children who continue to suck their thumbs as they get older are often the target of teasing from their friends and siblings. In many cases, this peer pressure alone is enough to make them stop. Pediatricians sometimes suggest that a parent place a plastic strip or an adjustable plastic cap called a “thumb guard” over the thumb to prevent the child from sucking on it. Over-the-counter agents are available that can be applied to the thumb. These cause a bitter taste when the thumb is sucked.