Mistletoe (Viscum and Phoradendron) in Pets

Mistletoe can cause vomiting and, in larger amounts, a slow heart in pets. Learn the difference between European and American mistletoe and what to tell your vet.

What It Is

Mistletoe is a parasitic evergreen that grows on tree branches and is hung as a holiday decoration. European mistletoe (Viscum album) contains viscotoxins and lectins; American mistletoe (Phoradendron species) contains phoratoxins. These proteins can irritate the gut and, in larger amounts, affect blood pressure and heart rate.

Where Pets Come Across It

Sprigs hung over doorways, wreaths and decorations, and fallen white berries on the floor during the holidays. Wild mistletoe grows on trees such as apple, poplar and oak.

Which Animals Are Affected

Dogs and cats, as well as horses and livestock.

Published Toxic Dose

No owner-usable mg/kg threshold is published. Poison centres generally report stomach upset after small amounts, with more serious signs after larger ingestions. The calculator does not attach a risk tier to the dose.

Signs and How Soon They Appear

Vomiting, drooling, diarrhoea and abdominal pain within a few hours. Larger amounts may cause weakness, a slow heart rate, low blood pressure, wobbliness and, rarely, collapse.

What to Do Right Now

Call your vet or a poison line with the number of berries or leaves eaten. Bring a sprig, as types differ. Do not induce vomiting at home.

European and American mistletoe compared

European mistletoe (Viscum album) has paired yellowish-green leaves and sticky white berries and grows on apple, poplar and lime trees. American mistletoe (Phoradendron species) has broader leaves and white berries and grows on oaks and other hardwoods across the southern and eastern US. Their proteins differ, and reports suggest European mistletoe may be more potent, but both should be treated as toxic. Artificial mistletoe is common and is not poisonous, but its plastic berries can block the gut if swallowed. Hang real sprigs high, check the floor beneath them each day, and throw out decorations after the holidays rather than leaving them where pets can find dried berries.

Mistletoe in herbal products

European mistletoe extracts are sold as herbal supplements and, in some countries, used in complementary cancer therapy for people. These products are concentrated and their effects on pets are not well studied, so a pet that chews a bottle or swallows tablets or injection vials should be treated as a possible poisoning. Bring the product to the vet. Mistletoe teas and tinctures should also be kept out of reach, and never given to a pet as a home remedy.

Frequently Asked Questions

Sources and References

• Pet Poison Helpline: Mistletoe
• Merck Veterinary Manual: Houseplants and Ornamentals (Phoradendron)

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