Is Barnaby's Thistle Toxic to Dogs and Cats? (2026)

This is a chronic grazing-exposure risk for horses (nigropallidal encephalomalacia), not a single-bite emergency — contact a vet if a horse has had ongoing pasture access to this weed. Not established as toxic to dogs or cats.

The toxic component in Barnaby's Thistle is sesquiterpene lactones (cause a neurological condition in horses called "chewing disease" from prolonged grazing).

Barnaby's Thistle causes a specific, irreversible neurological condition in horses (nigropallidal encephalomalacia, sometimes called 'chewing disease') from weeks of continuous grazing — it is not established as a dog or cat hazard, making this one of the few plants on this site where the horse risk profile is entirely different in kind, not just degree, from any risk to companion animals.

Scientific name

Centaurea solstitialis

Family

Compositae

Also known as

Barnaby's Thistle, Yellow Star Thistle

Typically found

outdoor