In all of Ireland, female fairies have quite a difficult time during childbirth.  In fact, many of the children born to fairies are born with deformities or stunted growth.  Of those that survive, many of them are traded off or exchanged for human children unbeknownst to the human parents. 

Adult fairies are repelled by their ugly offspring and have no love for them.  Whereas they will keep a child that is born without any defects, they cannot abide to keep one that is so deformed.  Therefore, at first chance, they will exchange or swap the deformed fairy child with a human one who they steal from the world of the mortals. 

Human children who have not yet been baptized or who are thought to be exceptionally beautiful and intelligent are most at risk of kidnapping.  The human parents are none the wiser for the uneven exchange.  However, such a terrible trade influences the entire household for the remainder of their lives. 

The fairy child that is left in the human household is a changeling who possesses great power.  The changeling is ill mannered, disagreeable, and ill tempered.  Even if the child for whom a changeling is switched was a happy and loving child, the changeling is nothing like him.  Rather, the changeling is only happy when others in the home are unhappy, particularly if some tragedy has befallen on the household.

The changeling is quite an annoyance and howls or cries throughout the daylight hours, causing all kinds of disturbances.  The crying is so loud and discordant that the humans can barely put up with it.  The changeling always appears to be miserable except in times of distress for the rest of the household.

In addition to being a discarded fairy child, changelings can actually be senile fairies who have been disguised as a child.  Moreover, changelings have also come from inanimate objects.  In particular, a piece of wood placed under a magical fairy spell can take on the appearance or guise of a child to join the human household in place of the real child.  This type of changeling is referred to as a stock.

Changelings typically have distinctive characteristics that can include yellowish skin, extremely dark eyes, and an unattractive, wrinkled face.  Plus, changelings have paper like skin and their face portrays wisdom far beyond their supposed human years.  Quite often, changeling will retain a physical deformity such as a lame leg, crooked hand, or misshapen back. 

Once the changeling is in the home, he undergoes physical transformations after about two weeks have passed.  He will grow a full set of teeth.  His legs will lengthen and become as thin as chicken bones.  Additionally, his hands will become curved like the talons of a bird of prey and they will become covered with a fine, downy hair.

Unfortunately, for the human household where a changeling is secretly placed, misfortune will rule the rest of their lives.  The changeling drains away all good fortune dispersing it like so much air.  Those who live within the household will be poor and miserable due to this horrible little creature that has taken control of their very lives.

About the only decent characteristic that a changeling might have is an aptitude for music.  As the changeling matures, he may show an interest in music, particularly the Irish pipes or fiddle.  However, even though his audience will be enthralled with his skillful playing, he only seems to play music or tunes from long ago.  All in all, the humans would have been much better off with their own child.