Thumb sucking at a young age, particularly before children begin teething, is completely natural and will not harm your child’s teeth. In fact, thumb sucking is actually okay as long as the behavior is stopped before a child’s permanent teeth begin to come in. After the age of five or six, thumb sucking and pacifier use can begin to affect the position of a child’s teeth. Prolonged thumb sucking can change the position of a child’s teeth, resulting in malocclusion of the teeth.