From Lady Wilde, Ancient Legends of Ireland, pages 48-49.
he fairy doctors are generally females. Old women, especially, are considered to have peculiar mystic and supernatural power. They cure chiefly by charms and incantations, transmitted by tradition through many generations; and by herbs, of which they have a surprising knowledge.
The fairies have an aversion to the sight of blood; and the peasants, therefor, have a great objection to being bled, lest "the good people" would be angry. Besides, they have much more faith in charms and incantations than in any dispensary doctor that ever practised amongst them.