Is Rhododendron Toxic?

Rhododendrons can indeed be toxic to humans and animals such as horses, cats and dogs. The poison is a grayanotoxin, also sometimes referred to as andromedotoxin, acetylandromedol or rhodotoxin. It is found in both the leaves and the flower nectar of the plant. With over 250 species of the plant found across the US and 800 species worldwide, gardeners, parents and pet owners should be aware of the plant's toxicity.

The toxin in rhododendrons is found in nearly all parts of the plant. In particular, it is concentrated in the flower nectar and leaves. Symptoms will normally begin to arise within two hours of ingestion. However, the toxin is rarely fatal. Instead, the symptoms typically last about two days.

To be toxic, the poison has to be digested in high enough amounts. Approximately 3 ml of toxin per kg(1.4 ml per lb.) of body weight is needed to produce a toxic effect. Put another way, a 55-pound child would need to eat over 100 grams (.2 lbs) of azalea or rhododendron leaves before reaching toxic levels. However, some animals such as horses or goats may easily consume enough foliage to be in danger from the toxin.

When the toxin is ingested, it bonds to and affects the membranes of the body's cells. The result can be excess salivation, muscular weakness, loss of or impaired vision and digestive symptoms, such as stomach irritation and abdominal pain. In severe cases, the heart's rate and rhythm can be affected and can lead to convulsions, stupor, paralysis, coma or even death.

Emergency medical treatment should be sought for children, adults or animals that ingest the leaves or flowers of the plant. Detoxification may include inducing vomiting and administering activated charcoal. Other treatment may include oxygen or other respiratory assistance, fluid replacement and drugs to address heart symptoms if the heart is affected.