Prevention being better than cure, a number of protections may be placed around an infant's cradle to ward off a changeling. A holy crucifix or iron tongs placed across the cradle will usually be effective, because fairies fear these. An article of the father's clothing laid across the child as it sleeps will have the same effect.

Changelings have prodigious appetites and will eat all that is set before them. The changeling has teeth and claws and does not take the breast like a human infant, but eats food from the larder. When the creature is finished each meal, it will demand more. Changelings have been known to eat the cupboard bare and still not be satisfied. Yet no matter how much it devours, the changeling remains as scrawny as ever.

Changelings do not live long in the mortal world. They usually shrivel up and die within the first two or three years of their human existence. The changeling is mourned and buried, but if its grave is ever disturbed all that will be found is a blackened twig or a piece of bog oak where the body of the infant should be. Some live longer but rarely into their teens.

There can also be adult changelings. These fairy doubles will exactly resemble the person taken but will have a sour disposition. The double will be cold and aloof and take no interest in friends or family. It will also be argumentative and scolding. As with an infant, a marked personality change is a strong indication of an adult changeling.

Changelings may be driven from a house. When this is achieved, the human child or adult will invariably be returned unharmed.

The least severe method of expulsion is to trick the fairy into revealing its true age. Another method is to force tea made from lusmore (foxglove) down the throat of a suspected changeling, burning out its human entrails and forcing it to flee back to the fairy realm. Heat and fire are anathema to the changeling and it will fly away.