Is St John’s Wort Toxic to Dogs?
Also known as: Hypericum perforatum, Klamath Weed, Goatweed · Hypericum perforatum
What makes it toxic
Hypericin, a photodynamic compound, plus hyperforin. Ingested hypericin reacts with sunlight in the skin, and the plant tissue irritates the GI tract.
Warning signs to watch for
Vomiting, diarrhea and drooling within hours; in the days after, inflamed, itchy skin on light-colored areas, nose and eyelids after sun exposure.
What to do if your dog eats it
Remove plant material, offer water and limit sun exposure for several days. Call your vet if vomiting continues or skin lesions appear.
Common questions
Is the yellow flower dangerous to touch or only to eat?
Contact alone rarely causes problems; ingestion followed by sun exposure is the toxic pattern. Dogs that graze it are the ones at risk.
Why is it called Klamath weed — was it a livestock problem?
Yes — it once poisoned grazing livestock with photosensitization across the American West, which is why biological control beetles were introduced against it.
More plants checked for dogs
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.