Thumb sucking is one of the most common habits of children. Between 50 and 87 percent of children suck their thumbs. The habit starts early in life, with 90 percent of children doing some form of hand sucking by the time they are 2.
- Thumb sucking is normal in infants and young children and should cause no permanent problems if it's not continued past age 5.
- Likewise, it's generally harmless for infants to use pacifiers.