The tooth fairy is a legendary good fairy who collects teeth as children lose them, offering coins in exchange. She is part of a large and complex cultural tradition of good and bad fairies, and children all over the world leave teeth for the tooth fairy in the hopes of seeing some money in the morning. In some cultures, instead of money, children receive a treat or a toy from the tooth fairy, with some spoilsport tooth fairies leaving presents like toothbrushes or floss to encourage children to take care of their budding adult teeth.
Before delving into the story of the tooth fairy, you might be interested in hearing some background. Many cultures have a long history of superstition surrounding the loss of the milk teeth, the teeth which children use in their early years. In some societies, the loss of the milk or “baby” teeth is viewed as a rite of passage, with the loss of the teeth signaling a transition into adulthood. A history of performing some sort of ritual act with lost teeth is ancient.
Tied in with beliefs about the loss of the milk teeth are beliefs about witchcraft. Many cultures used to believe (and some still do) that if a witch manages to obtain a part of someone's body, he or she can use that body part to perform black magic. Milk teeth would be a prime target for witches, along with things like fingernail clippings and scraps of hair. As a result, many cultures had a tradition of putting milk teeth into safekeeping to ensure that they would not enter the hands of witches.
Historically, some people buried milk teeth, fed them to animals, or saved them so that they could keep an eye on them. As early as the 1600s, legends about fairies who collected baby teeth began to arise, but it wasn't until the early 1900s that people started leaving offerings for the tooth fairy. This good fairy is supposed to take care of lost milk teeth, ensuring that their owner grows up healthy and strong.
The tradition of leaving money behind in exchange for a tooth also reflects very old beliefs about fairies. In English folklore especially, there is a long tradition of leaving gifts for fairies and receiving presents in return. The fairies are in a sense rewarding the people who offer them assistance, and in the case of the tooth fairy, the money is an expression of thanks for the tooth, and a reward for bearing the discomfort associated with losing milk teeth.