Thumb sucking is a normal behavior. Well, sucking your own thumb is normal. If you are sucking someone else’s, that’s a little weird! Thumb sucking only becomes a problem if it continues for too long. It can begin during the fetal period, but should be curtailed by the time that permanent teeth come in. permanent teeth begin to sprout around age six. If thumb sucking continues past this age, your child can develop an overbite or buckteeth.

There are other problems that come along with late thumb sucking. An article in 1993 in the journal Pediatrics looked at the “influence of thumb sucking on peer social acceptance in first grade children.” They found that thumb-sucking children were judged as less intelligent, happy, attractive, likable, and fun and less desirable as a friend, playmate, seatmate, classmate, and neighbor than the nonsuckers.

So if buckteeth aren’t bad enough, social ostracism is yet another reason to quit the thumb.