It is normal for babies to suck because it helps them relax.
By the time your child is two or three years of age, he or she has less need to suck. If your child still likes to suck, a soother is better than sucking a thumb. Why? Because you can control when and how your child uses a soother. You can't control a thumb going into the mouth.
Never put sugar, honey or corn syrup on a soother. They can cause cavities. It's best to get your child to stop sucking before permanent teeth come in, at about age five. If a child keeps sucking a soother or thumb after the permanent teeth have come in, it could cause problems with how the jaw and teeth grow. This can lead to the front teeth not touching each other, what is know as an open bite. Furthermore, crowding of teeth can occur needing braces or Invisalign.
