PlantFunImperforate St. John's-wort Toxic?
Hypericin is the primary toxic compound driving photosensitivity reactions, with ~20% of toxicity remaining even in dried hay/forage
Horses are uniquely sensitive to poisoning, with elevated risk of severe complications including infection-prone lesions and coma
All plant parts are toxic, with the highest concentrations of active compounds found in flowers and leaves
FAQ
Is Imperforate St. John's-wort toxic to Humans?
No confirmed human toxicity data available from provided sources; high dose ingestion may cause mild photosensitivity reactions (Low)
Is Imperforate St. John's-wort toxic to Cats?
No specific feline poisoning cases or symptoms documented in available datasets (Low)
Is Imperforate St. John's-wort toxic to Dogs?
No specific canine poisoning cases or symptoms documented in available datasets (Low)
Is Imperforate St. John's-wort toxic to Horses?
Photosensitive dermatitis (redness, edema, black crusts) on sun-exposed unpigmented skin, infection-prone lesions, loss of appetite, uncoordinated movement, restlessness, convulsions, coma in severe cases (Moderate)
Toxicity Details
No confirmed human toxicity data available from provided sources; high dose ingestion may cause mild photosensitivity reactions
No specific feline poisoning cases or symptoms documented in available datasets
No specific canine poisoning cases or symptoms documented in available datasets
Photosensitive dermatitis (redness, edema, black crusts) on sun-exposed unpigmented skin, infection-prone lesions, loss of appetite, uncoordinated movement, restlessness, convulsions, coma in severe cases
Toxicity Snapshot
First Aid & Prevention
First 30 Minutes
- • Immediately move affected animals out of direct sunlight into a fully shaded enclosed stall
- • Remove all access to Hypericum plant material and potentially contaminated forage
- • Rinse sun-exposed unpigmented skin areas with cool clean water to remove residual plant compounds
Contact Vet Immediately
- • Visible skin lesions, blisters, or dark crusting appear on unpigmented sun-exposed skin
- • Neurological symptoms present, including restlessness, uncoordinated movement, or convulsions
- • Animal shows loss of appetite, lethargy, or reduced responsiveness after suspected ingestion
Prevention
- • Regularly inspect pastures and hay supplies to remove all Hypericum species growth
- • Restrict grazing access for livestock (especially horses) to areas with known wild Hypericum populations
- • House light-colored/unpigmented livestock indoors during peak sun hours if Hypericum contamination is suspected
Treatment & Prognosis
- • Administer standard decontamination and symptomatic care per plant poisoning emergency protocols
- • Use prescribed antibiotics with glucocorticoids (local or parenteral) as directed by a veterinarian
- • Administer zinc-cod liver oil paste and niacin supplements per veterinary guidance
- • Note that antihistamines have limited efficacy for treating this type of poisoning
Professional Toxicology
• Hypericin accumulates in skin tissue after ingestion, triggering phototoxic reactions when exposed to UV sunlight
• High doses of active compounds exert mild neurotoxic effects leading to neurological symptoms in sensitive species
Information from CliniTox veterinary text.
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Data Sources
This information is for reference only and does not constitute medical advice. If ingestion or poisoning is suspected, seek medical or veterinary attention immediately.