[5] European mistletoe is the only multicellular organism known to lack a functioning respiratory complex I in its electron transport chain, a protein that is essential for the creation of useful energy for its cells.

[6] It is believed to survive by obtaining adenosine triphosphate and energy-rich compounds from its host as well as reorganizing its other respiratory complexes and slowing its growth and energy requirements.

[15][16] Some birds have immunity to the toxin and enjoy the berries, especially the mistle thrush that is so named because mistletoe is their favourite food.

In cultures across pre-Christian Europe, mistletoe was often seen as a representation of divine male essence (and thus romance, fertility, and vitality).

[17] Mistletoe figured prominently in Greek mythology, and is believed to be the Golden Bough of Aeneas, ancestor of the Romans.

[23] When Christianity became widespread in Europe after the third century AD, the ancient religious or mystical respect for the mistletoe plant was absorbed only as a cultural tradition.

The earliest documented evidence of the tradition of kissing under the mistletoe dates from sixteenth century England, a custom that was apparently very popular at that time.

Winston Graham reports a Cornish tradition that mistletoe was originally a fine tree from which the wood of the Cross was made, but afterward it was condemned to live on only as a parasite.

(The similar native species Phoradendron leucarpum is used in North America in lieu of the European Viscum album.)

[27] It was alluded to as common practice in 1808[28] and described in 1820 by American author Washington Irving in his The Sketch Book of Geoffrey Crayon, Gent.

: The mistletoe is still hung up in farm-houses and kitchens at Christmas, and the young men have the privilege of kissing the girls under it, plucking each time a berry from the bush.

[29]In Germany, the Christmas tradition is that people who kiss under mistletoe will have an enduring love or are bound to marry one another.

[32] The sticky juice of mistletoe berries was used to make birdlime, an adhesive to trap small animals or birds.

[34] Mistletoe leaves and young twigs are used by herbalists and preparations made from them are popular in Europe, especially in Germany, for attempting to treat circulatory and respiratory system problems.