A human child might be taken due to many factors: to act as a servant, the love of a human child, or malice. Most often it was thought that fairies exchanged the children. Some Norwegian tales tell that the change was made to prevent inbreeding: to give trolls and humans new blood, humans were given children with enormous strength as a reward. In some rare cases, the very elderly of the Fairy people would be exchanged in the place of a human baby, and then the old fairy could live in comfort, being coddled by its human parents. Simple charms, such as an inverted coat or open iron scissors left where the child sleeps, were thought to ward them off; other measures included a constant watch over the child.
Purpose of a changeling Edit
Some people believed that trolls would take unbaptized children. Once children had been baptized and therefore become part of the Church, the trolls could not take them. One belief is that trolls thought that being raised by humans was something very classy, and that they therefore wanted to give their own children a human upbringing.
Beauty in human children and young women, particularly blond hair, attracted the fairies.
In Scottish folklore, the children might be replacements for fairy children in the tithe to Hell; this is best known from the ballad of Tam Lin. Also, according to common Scottish myths, a child born with a caul (head helmet) across their face is a changeling, and of fey birth.
Some folklorists believe that fairies were memories of inhabitants of various regions in Europe who had been driven into hiding by invaders. They held that changelings had actually occurred; the hiding people would exchange their own sickly children for the healthy children of the invaders.
In other folklore, the changelings are put in place of the child to feed off of the mother of the child. The kidnapped child then becomes food for the changeling's mother. This is done for the survival of their kind. Once the changeling mother and the changeling have drained the life from the human mother and child, the changeling and its mother begin to search for a new suitable food source. Other sources say that human milk is necessary for fairy children to survive. In these cases either the newborn human child would be switched with a fairy babe to be suckled by the human mother, or the human mother would be taken back to the fairy world to breastfeed the fairy babies. It is also thought that human midwives were necessary to bring fairy babes into the world.
Some changelings might forget they are not human and proceed to live a human life. Changelings which do not forget, however, may later return to their fairy family, possibly leaving the human family without warning. As for the human child that was taken, he or she may often stay with the fairy family forever.