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Mistletoe Poisoning

Medically Reviewed by Dany Paul Baby, MD on November 04, 2022

When Thanksgiving is over and the holiday music starts to play on the radio, it’s time to haul out the seasonal decorations. The winter holiday season typically involves several types of decorative plants, like Christmas trees, holly, poinsettias, and mistletoe. 

You may have heard that some of these plants are dangerous to consume. To an extent, that’s true. Below, we’ll discuss how toxic mistletoe actually is.

What Is Mistletoe?

Mistletoe is a plant that often plays a role in Christmas decorations, but in nature, it’s a type of parasitic shrub. Mistletoe survives by digging its roots into a tree and siphoning nutrients and minerals. Mistletoe are not “true” parasites but “hemi parasites” because most of them can photosynthesize on their own. As the mistletoe plants grow, they become a thick tangle of branches that earns them the nickname “witches' broom.”

In the U.S., mistletoe are most often found on black gum, hickory, oak, pecan, and red maple trees. Most healthy trees can manage a few mistletoe infestations, but too many can cause the trees to become weak, especially in situations like disease or drought.  

Despite being a parasite, mistletoe are important to the environment. Their berries feed several species of birds, and three species of butterfly are dependent on mistletoe for survival. Mistletoe also provides nectar and pollen for bees when few other sources are available. Animals like cattle, deer, elk, and several species of insects feed on the mistletoe plant.

There are about 1,300 species of mistletoe around the world. The type of mistletoe that makes its appearance during the holiday season is Phoradendron serotinum, or American mistletoe. This species grows in North America but is sold around the world. It grows small white flowers in the spring followed by white berries.

Species of mistletoe can be found worldwide and include:

  • Big leaf mistletoe (Phoradendron tomentosum): It is used in Christmas decorations, though less frequently than American mistletoe. Big leaf mistletoe grows in the western U.S.
  • Desert mistletoe (Phoradendron californicum): This type of mistletoe is found in the southern U.S. It has scale-like leaves, tiny yellow-green flowers, and pink, red, or white fruits.
  • Dwarf mistletoe (Arceuthobium genus): Dwarf mistletoe are a fully parasitic species of mistletoe that feed exclusively on conifers like pine, cedar, and spruce trees. Dwarf mistletoe will eventually kill the tree they feed off of.
  • European mistletoe (Viscum album): This species of mistletoe is found throughout Europe, north Africa, central Asia, and Japan, and is the species traditionally celebrated in Europe. Like American mistletoe, it has white berries, but the flowers of European mistletoe are yellowish-green.

Throughout history, European mistletoe has been used to treat arthritis, asthma, dermatitis, epilepsy, headaches, hypertension, infertility, rheumatism, seizures, and symptoms of menopause. Some believe it could be used as a cancer treatment, but there has not yet been a study that has proved this to be the case. Despite this, mistletoe extract is one of the most prescribed therapies for cancer patients in Europe.

How to Identify Mistletoe

There are over a thousand species of mistletoe, and some of them look very different from the mistletoe we associate with Christmas. Most of them share some similarities that make mistletoe identification easy but not all.

American mistletoe bunches can grow up to three feet across. The leaves alternate and are round, leathery, thick, and green. Both the flowers and berries are small and white, and the berries are covered in a sticky substance that makes them more enticing to birds.

On the other hand, quintral (Tristerix aphylla), a mistletoe species native to Chile, looks completely different. This type of mistletoe uses cacti as a host instead of trees. In the winter, the quintral’s red flowers burst through the skin of the cactus. The flowers are made of long tubes, and look a little like sea anemones. Quintral produces pale pink berries that are eaten by Chilean mockingbirds.

The things that the various species of mistletoe have in common are that they are either fully or hemiparasitic, and they produce berries. Most grow bush-like plants onto their host. The hosts are usually trees, but can sometimes be shrubs, or, as in the case of the quintral mistletoe, cacti.

Is Mistletoe Poisonous?

There has long been concern about the toxicity of mistletoe. There’s a long history detailing the side effects of mistletoe poisoning. But those poisonings involve European mistletoe, not American mistletoe.

Studies have shown that few people have symptoms after eating the berries or leaves of American mistletoe, and no patients observed by these studies died. One study found a very small amount of patients had stomach upset after eating a few leaves.

European mistletoe seems to be more toxic. While it has been used medicinally, highly concentrated doses can cause severe illness.

Mistletoe Poisoning

All parts of American mistletoe contain a toxic protein called phoratoxin. Most times, if someone ingests a small amount of American mistletoe, they won’t have any symptoms. Those that do have mistletoe poisoning symptoms usually have gastrointestinal symptoms like nausea and vomiting. 

Like American mistletoe, the entire European mistletoe plant is toxic, though the berries have very low amounts of toxin. European mistletoe contains viscotoxins, which prevent new cells from forming. This can be dangerous for areas of the body with rapid cellular turnover, like the gastrointestinal tract. 

A few hours after European mistletoe poisoning, you may start to have gastrointestinal symptoms. The tissue of the gastrointestinal tract may start to die off without new cells to replace old ones. Other symptoms of European mistletoe poisoning include:

  • Central nervous system damage
  • Delirium
  • Kidney damage
  • Liver damage
  • Slow heart rate (bradycardia)
  • Death

Death due to mistletoe poisoning is rare. When it does happen, it’s usually caused by drinking brewed tea containing mistletoe.

What to Do If You Have Mistletoe Poisoning

If you believe you or a loved one has swallowed mistletoe, contact Poison Control through their website or their toll-free hotline at 1-800-222-1222. They’ll take information like the patient’s age, weight, the amount of mistletoe swallowed, the part of the plant that was swallowed, how long ago the plant was swallowed, and their current symptoms. They’ll use that information to determine if you need to seek medical care.

There is no specific mistletoe poisoning treatment. If you’re at the hospital, they will likely monitor your vital signs like heart rate and breathing. They may provide fluids to prevent dehydration or medication to manage symptoms like severe vomiting.

Safe Plants that Look Like Mistletoe

Mistletoe species are fairly unique, and it’s unlikely that they would be mistaken for something else. While they aren’t the only parasitic plants, the tangled bush they grow on their trees and their sticky berries make them stand out.

Show Sources

SOURCES:
Calscape: “Phoradendron leucarpum.”
iNaturalist: "Red Sea Anemone or Kōtore / Kōtoretore."
Lady Bird Johnson Wildflower Center: “Phoradendron leucarpum.”
National Cancer Institute: “Mistletoe Extracts (PDQ®)–Patient Version.”
National Center for Complementary and Integrative Health: “European Mistletoe.”
National Wildlife Federation: “12 Things to Know about Mistletoe.”
North Carolina State University Cooperative Extension: “Does Mistletoe Harm Trees?”
Plants for a Future: “Viscum album.”
Poison Control: “Is mistletoe poisonous?”
United States Geological Survey: “Not Just for Kissing: Mistletoe and Birds, Bees, and Other Beasts.”
University of Wisconsin Horticulture Division of Extension: “Mistletoe.”
Western Journal of Emergency Medicine: “Holiday Plants with Toxic Misconceptions.”

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