Rhododendrons and azaleas (grayanotoxins) in Pets

Rhododendron and azalea grayanotoxins can slow a pet's heart after only a few leaves. Learn why there is no published dose, the signs to watch and why 'mad honey' is also toxic.

What It Is

Rhododendrons and azaleas belong to the heath family and contain grayanotoxins, which keep sodium channels in nerve and heart cells open. The result is vomiting, weakness and a slow heart. The Merck Veterinary Manual notes that the toxins are found in all parts, including pollen and nectar, so 'mad honey' made from these flowers is toxic too.

Where Pets Come Across It

Garden shrubs and potted indoor azaleas, especially in spring. Mountain laurel and Japanese pieris contain the same toxins.

Which Animals Are Affected

Dogs, cats, goats, sheep, cattle, horses and birds. Pet Poison Helpline notes that severe signs are expected with large ingestions, such as grazing goats, but may occur in cats or dogs that eat only a few leaves or flowers.

Published Toxic Dose

No mg/kg threshold is published for pets. Grayanotoxin content varies widely between species and hybrids. The calculator shows no risk tier for it.

Signs and How Soon They Appear

Drooling, vomiting, diarrhoea and weakness usually start within a few hours. More serious poisoning brings a slow or irregular heart rate, low blood pressure, wobbliness, tremors, collapse and, rarely, coma.

What to Do Right Now

Call your vet or a poison line with the number of leaves or flowers eaten. Bring a sample. Do not make your pet vomit at home.

Rhododendrons, azaleas and their relatives

Rhododendrons are large evergreen shrubs with leathery leaves and big trusses of flowers in spring; azaleas are a group within the same genus, usually smaller, and often sold in pots as gifts. Mountain laurel (Kalmia), Japanese pieris and fetterbush belong to the same family and also contain grayanotoxins. Goats, sheep and llamas are frequently poisoned when they browse garden shrubs or are given hedge clippings, and pet rabbits and guinea pigs are at risk if fed garden greens without identification. For dogs, the main risk is chewing leaves or flowers of a potted azalea. Never offer prunings to livestock, and keep potted azaleas in rooms pets cannot reach. Honey labelled as 'mad honey' is sold online as a novelty and should be kept away from pets.

Frequently Asked Questions

Sources and References

• Pet Poison Helpline: Rhododendron and Azalea
• ASPCA: Rhododendron
• Merck Veterinary Manual: Houseplants and Ornamentals Toxic to Animals

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