Infants have a natural reflex to suck on their thumbs and fingers. Babies use fingers or pacifiers to help them feel secure and or content. Thumb and finger sucking is also a relaxing habit for babies and toddlers that can help induce sleep. Thumb and finger sucking start to become a problem when it continues after the eruption of the permanent teeth. That’s because it can affect the growth of the mouth and the proper placement of the new teeth coming in. Pacifiers are no different; they affect the mouth in the same way; however, they can be easier to control than finger habits. A child should stop sucking their thumb between the ages of 2-4.