Mistletoe Toxicity Explained

Delicate green leaves and white berries of Mistletoe.
Delicate green leaves and white berries of Mistletoe. Jacky Parker Photography / Getty Images

Kissing under the mistletoe is a holiday tradition. Eating it is not, because mistletoe has a reputation as being poisonous. Yet many of us know someone who ate a berry or two as a kid and lived to tell the tale, so just how toxic is mistletoe?

The answer is: it depends on the type of mistletoe and what part you eat. There are several species of mistletoe. The Phoradendron species contain a toxin called phoratoxin, which can cause blurred vision, nausea, abdominal pain, diarrhea, blood pressure changes, and even death. The Viscum species of mistletoe contain a slightly different cocktail of chemicals, including the poisonous alkaloid tyramine, which produce essentially the same symptoms. Although mistletoe has therapeutic uses, eating any part of the plant (particularly the leaves or berries) or drinking a tea from the plant can result in sickness and possibly death. Unlike the holiday poinsettia, which has a bad reputation yet probably won't do more than make you feel sick if you eat it, mistletoe ingestion warrants a call to Poison Control and immediate medical attention.

Fortunately, most mistletoe found around the holidays is the less toxic species. A 1996 study found that only a fraction of patients from 92 cases of mistletoe ingestion showed symptoms. Eight of 10 people who ingested five or more berries were free of symptoms. Three of the 11 people who ate mistletoe leaves but no berries had upset stomachs, but no other symptoms. Children and pets are more at risk of poisoning because of their size and metabolism.