Thumb sucking is a common habit in infants and young children, often starting in the womb and providing comfort or self-soothing. While it is typically harmless in early childhood, prolonged thumb sucking past the age of 4 or 5 can cause dental issues, such as misaligned teeth or changes in the roof of the mouth. Psychologically, it may signal anxiety or stress in older children. Parents are encouraged to gently discourage the habit if it persists, using positive reinforcement or seeking professional advice if necessary. In most cases, children outgrow thumb sucking on their own by adolescence.