Is White Snakeroot Toxic to Cats?
Also known as: White Sanicle, Tall Boneset, Ageratina altissima · Ageratina altissima
What makes it toxic
Tremetol and related benzofuran ketones in leaves, stems and flowers. They impair energy metabolism in muscle and heart tissue; the toxin also passes into milk, historically causing milk sickness in humans.
Warning signs to watch for
Onset over hours to days: vomiting, lethargy, stumbling, muscle trembling, crouched stiff posture, then weakness, heart rhythm disturbance and collapse.
What to do if your cat eats it
Go to a vet promptly after any known ingestion, even before symptoms appear, and mention tremetol risk. There is no antidote — supportive care and monitoring of heart and muscles must start early.
Common questions
Is white snakeroot dangerous through milk or meat near my cat?
Cats are poisoned by eating the plant itself; livestock eating it pass tremetol into milk and meat, which caused human milk sickness. Keeping the weed out of any grazing area protects the whole chain.
Why did white snakeroot kill people in the 1800s but not usually today?
Commercial dairying separated cows from woodland weeds, ending milk-sickness epidemics. The plant itself is unchanged and just as dangerous to pets that chew it.
More plants checked for cats
This page is general educational information, not a substitute for professional veterinary advice. Every pet is different — if your animal ate something concerning, contact your veterinarian or a pet poison hotline right away. Checking what your pet can eat? Visit our sister site SafeOrToxic.