Dogs
Potentially toxicConsulted references classify the plant as toxic or irritating for that pet type.
Verified against ASPCA/provenance audit 2026-05-06 on May 6, 2026.
dog safety reference
Is St. John's Wort safe for dogs?
Hypericum perforatum
Klamath Weed is a perennial flowering plant known for its bright yellow blooms and medicinal history, but it contains compounds that can cause significant health issues if ingested by pets. It is widely recognized as a toxic plant that requires careful management in households with animals.
Common Saint John's WortGoatweedHypericum perforatumSt. John's Wort
- Light
- Full sun to partial shade
- Habit
- Upright, spreading perennial
- Care
- Low
Safety status
What this means for your dog
Dogs: hypericin is the active toxin, and the headline danger is photosensitive dermatitis — ulcerative, weeping skin damage on parts of the dog that take sun (nose, ear margins, belly) after ingestion or contact with the plant.
What to watch for
ASPCA reports photosensitization manifesting as ulcerative and exudative dermatitis. Watch for open, oozing sores on the nose, ear edges, and lightly furred skin, especially after time in the sun.
Time window
Specific onset and recovery timing are not documented in the ASPCA listing.
When to call the vet
Call when you see weeping or ulcerated skin lesions, persistent irritation, or progression after suspected exposure to the plant.
Sources: ASPCA (no first-aid guidance).
If a pet has chewed or swallowed plant material and is showing symptoms, contact a veterinarian or poison resource immediately. This product is for structured reference, not diagnosis.
Dogs — concern notes
Common signs
Photosensitivity, dermatitis, gastrointestinal upset, and lethargy.
Escalation note
The plant contains hypericin, which can cause increased sensitivity to light and skin inflammation. Seek veterinary care promptly if ingestion is observed or suspected.
Safer alternatives
No hand-picked alternatives for this plant yet. You can still pick your own using the Compare button on any other plant.
Source evidence
NC State Extension Plant Toolbox
botanical · 94% reliability
Hypericum perforatum is a perennial herb that is considered toxic to livestock and pets.
Questions about St. John's Wort
Is St. John's Wort toxic to dogs?
Yes, St. John's Wort (Hypericum perforatum) is toxic to dogs. It contains hypericin, a compound that can cause photosensitivity, dermatitis, gastrointestinal upset, and lethargy if ingested.
What are the symptoms of St. John's Wort poisoning in dogs?
The most distinctive symptom is photosensitization — hypericin makes dogs abnormally sensitive to sunlight, which can cause ulcerative and exudative dermatitis (open, oozing sores) on the nose, ear edges, and areas with thin fur. Dogs may also show gastrointestinal upset and lethargy.
What should I do if my dog ate St. John's Wort?
Contact your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435 immediately. Keep your dog out of sunlight, as hypericin increases light sensitivity and sun exposure can worsen skin damage. Seek veterinary care promptly if ingestion is observed or suspected.
What part of St. John's Wort is dangerous to dogs, and why?
The entire plant contains hypericin, a photosensitizing compound that causes increased sensitivity to light and skin inflammation. This mechanism is what distinguishes St. John's Wort toxicity — the harm can be compounded by sunlight exposure after ingestion, triggering weeping skin lesions especially on lightly furred or unpigmented areas.
Same dog verdict
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