St. John's wort

Hypericum perforatum L.

Hypericaceae // flowering aerial parts

Safety warning on record — see Safety

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Uses & evidence

Uses and evidence recorded

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Preparation

infusion/tea, tincture, powder/capsule, extract

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Safety

Safety cautions recorded

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Research

No linked research on file

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Overview

Plant parts

flowering aerial parts

Known constituents

hyperforin, hypericins, flavonoids

Research corpus coverage

Materia medicaPet safety

Chemistry notes

CHEMISTRY: Relevant reported constituents include hyperforin; hypericins; flavonoids; constituent presence alone does not establish clinical efficacy.

Uses & Evidence

Traditional / historical use

Documented traditional use — not a claim of established efficacy.

TRADITIONAL: St. John's wort has been used for low mood; wounds; this records historical/traditional use and does not establish efficacy.
MODERATE · evidence synthesis/fact sheet · NCCIH Herbs at a Glance

Modern evidence

EVIDENCE: For the major use set (low mood; wounds), the evidence assessment is well-supported: Well-supported for mild-to-moderate depression in systematic reviews of standardized extracts; not established for severe depression.
HIGH · systematic review/meta-analysis · Cochrane: St. John's wort for treating depression

Preparation

Forms used traditionally

infusion/teatincturepowder/capsuleextract

A listed form does not imply it suits every plant part, or that one preparation is interchangeable with another — see the plant’s own notes below.

PREPARATION: The medicinal material is flowering aerial parts; traditional and modern forms include infusion/tea, tincture, powder/capsule, extract. No dose or potency is specified.
MODERATE · regulatory monograph · EMA European Union herbal monographs and list entries
Preparation-specific evidence should not be generalized across extracts, teas, oils, or whole herb.

Safety

Cats

High risk
ASPCA designates St. John’s wort (*Hypericum perforatum*; family Clusiaceae) as toxic to cats; hypericin can cause photosensitization with ulcerative and exudative dermatitis.
Intrinsic toxicity · UNKNOWN · Not specified; no preparation distinctions provided · HIGH · poison_control_database · St. John's Wort - Toxic and Non-toxic Plants

Dogs

High risk
ASPCA designates St. John’s wort (*Hypericum perforatum*; family Clusiaceae) as toxic to dogs; hypericin can cause photosensitization with ulcerative and exudative dermatitis.
Intrinsic toxicity · UNKNOWN · Not specified; no preparation distinctions provided · HIGH · poison_control_database · St. John's Wort - Toxic and Non-toxic Plants
Caution
St. John’s wort (Hypericum perforatum) is listed under “Plants Toxic to Dogs.” No cat-specific evidence, toxic constituents, clinical signs, or preparation distinctions are provided.
Intrinsic toxicity · UNKNOWN · Not stated; whole plant or plant group listing only · HIGH · poison_control_database · Toxic and Non-Toxic Plant List — Dogs - ASPCA

Cats & dogs

High risk
St. John’s wort may cause photosensitivity, increased prothrombin time, gastrointestinal upset, dry mouth, headache, nausea, or neuropathy and commonly causes herb-drug interactions; serotonin syndrome may occur with SSRIs.
Interaction · OTHER · St. John’s wort product · MODERATE · veterinary_manual · Herbal Medicine in Veterinary Patients - Therapeutics
Caution
St. John’s wort (Hypericum perforatum) is listed as an herbal therapy that should be disclosed to the veterinarian and used with caution when given with fluoxetine; the page does not provide plant-preparation details or identify a toxic constituent.
Intrinsic toxicity · UNKNOWN · Not stated · HIGH · veterinary_hospital_guidance · Fluoxetine | VCA Animal Hospitals
Caution
Oral St. John’s wort preparations (capsule, liquid, powder, or tablet) may cause vomiting, diarrhea, dry mouth, skin redness, itching, and sun sensitivity; allergic reactions may include irregular breathing, rash, fever, facial puffiness, or swelling.
Allergy · ORAL · capsule, liquid, powder, or tablet · HIGH · veterinary_hospital_guidance · St. John's Wort | VCA Animal Hospitals
Caution
St. John’s wort should be used cautiously with numerous medications, including antidepressants and antianxiety drugs, antifungals, antihistamines, antihypertensives, antivirals, benzodiazepines, chemotherapeutics, cyclosporin, tacrolimus, digoxin, and warfarin or other blood thinners.
Interaction · ORAL · capsule, liquid, powder, or tablet · HIGH · veterinary_hospital_guidance · St. John's Wort | VCA Animal Hospitals
Caution
The page advises against use in pets allergic to any component, pregnant or nursing pets, and very young or very old pets; caution is advised in pets with liver, kidney, or heart disease.
Allergy · ORAL · capsule, liquid, powder, or tablet · HIGH · veterinary_hospital_guidance · St. John's Wort | VCA Animal Hospitals
Caution
Ingestion of St. John’s wort can cause mild central nervous system depression in animals; very large ingestions may cause serotonin syndrome.
Intrinsic toxicity · OTHER · herbal supplement; botanical identity and formulation not specified · HIGH · veterinary_manual · Toxicosis en animales por suplementos dietéticos y plantas ...
Caution
Most reported animal exposures to St. John's wort cause mild central nervous system depression; very large ingestions can cause serotonin syndrome with vocalization, dysphoria, tachycardia, tremors, seizures, and hyperthermia.
Intrinsic toxicity · OTHER · preparation not specified · HIGH · veterinary_manual · Toxicosis en animales por suplementos dietéticos y a base ...
Caution
Most animal cases of St. John’s wort ingestion involve mild central nervous system depression. Very large ingestions can cause serotonin syndrome with vocalization, dysphoria, tachycardia, tremors, seizures, and hyperthermia.
Intrinsic toxicity · OTHER · herbal supplement · HIGH · veterinary_manual · Toxicoses in Animals From Human Dietary and Herbal Supplements

Additional safety notes (general, unstructured)

Free-text safety notes carried from their source — not broken out by species, route, or hazard type, and not equivalent to the structured records above. Each note names the kind of source it came from.

SAFETY: Major issues include Photosensitivity; agitation; serotonin toxicity; withdrawal/relapse risk. Contraindications/cautions include Bipolar disorder; concurrent serotonergic therapy without oversight.
HIGH · observational/case series and expert review · LiverTox: Herbal and Dietary Supplements
SAFETY: Clinically relevant interaction concerns include Potent CYP3A4, CYP2C9, CYP2C19 and P-gp induction lowers exposure to oral contraceptives, transplant drugs, anticoagulants, antiretrovirals and many others; serotonergic interactions.
MODERATE · observational/case series and expert review · LiverTox: Herbal and Dietary Supplements
Some interactions are theoretical or based on case reports/pharmacokinetics rather than outcome trials.
SAFETY: Pregnancy/lactation reference: Avoid in pregnancy/lactation unless specifically medically supervised because interactions and safety uncertainties are substantial.
MODERATE · regulatory monograph or evidence synthesis · NCCIH Herbs at a Glance
Absence of evidence is not evidence of safety.
St. John’s wort (Hypericum perforatum) is listed as an herbal therapy that should be disclosed to the veterinarian and used with caution when given with fluoxetine; the page does not provide plant-preparation details or identify a toxic constituent.
HIGH · veterinary_hospital_guidance · Fluoxetine | VCA Animal Hospitals
The page addresses concomitant use with fluoxetine rather than intrinsic St. John’s wort toxicity and does not specify mechanism, preparation, or clinical signs attributable to the plant.
Oral St. John’s wort preparations (capsule, liquid, powder, or tablet) may cause vomiting, diarrhea, dry mouth, skin redness, itching, and sun sensitivity; allergic reactions may include irregular breathing, rash, fever, facial puffiness, or swelling.
HIGH · veterinary_hospital_guidance · St. John's Wort | VCA Animal Hospitals
The page does not classify St. John’s wort as toxic or non-toxic and provides no concentration-specific information.
St. John’s wort should be used cautiously with numerous medications, including antidepressants and antianxiety drugs, antifungals, antihistamines, antihypertensives, antivirals, benzodiazepines, chemotherapeutics, cyclosporin, tacrolimus, digoxin, and warfarin or other blood thinners.
HIGH · veterinary_hospital_guidance · St. John's Wort | VCA Animal Hospitals
The page lists medication classes and examples but does not provide interaction mechanisms, frequencies, or severity estimates.
The page advises against use in pets allergic to any component, pregnant or nursing pets, and very young or very old pets; caution is advised in pets with liver, kidney, or heart disease.
HIGH · veterinary_hospital_guidance · St. John's Wort | VCA Animal Hospitals
No cat-versus-dog differences or disease-specific clinical outcomes are provided.
Ingestion of St. John’s wort can cause mild central nervous system depression in animals; very large ingestions may cause serotonin syndrome.
HIGH · veterinary_manual · Toxicosis en animales por suplementos dietéticos y plantas ...
The page does not provide the botanical name, constituent, concentration, or species-specific toxicity comparison.
Most reported animal exposures to St. John's wort cause mild central nervous system depression; very large ingestions can cause serotonin syndrome with vocalization, dysphoria, tachycardia, tremors, seizures, and hyperthermia.
HIGH · veterinary_manual · Toxicosis en animales por suplementos dietéticos y a base ...
No toxic constituent is named; the source does not provide separate dog-versus-cat susceptibility data.
St. John’s wort may cause photosensitivity, increased prothrombin time, gastrointestinal upset, dry mouth, headache, nausea, or neuropathy and commonly causes herb-drug interactions; serotonin syndrome may occur with SSRIs.
MODERATE · veterinary_manual · Herbal Medicine in Veterinary Patients - Therapeutics
Hyperforin and hypericin were named but not explicitly identified as toxic constituents.
Most animal cases of St. John’s wort ingestion involve mild central nervous system depression. Very large ingestions can cause serotonin syndrome with vocalization, dysphoria, tachycardia, tremors, seizures, and hyperthermia.
HIGH · veterinary_manual · Toxicoses in Animals From Human Dietary and Herbal Supplements
The page does not identify a toxic constituent or state a cat-versus-dog toxicity difference.
ASPCA designates St. John’s wort (*Hypericum perforatum*; family Clusiaceae) as toxic to cats; hypericin can cause photosensitization with ulcerative and exudative dermatitis.
HIGH · poison_control_database · St. John's Wort - Toxic and Non-toxic Plants
The page does not explicitly state the exposure route or whether risk varies by preparation or concentration.
St. John’s wort (Hypericum perforatum) is listed under “Plants Toxic to Dogs.” No cat-specific evidence, toxic constituents, clinical signs, or preparation distinctions are provided.
HIGH · poison_control_database · Toxic and Non-Toxic Plant List — Dogs - ASPCA
Family is listed as Clusiaceae.
ASPCA designates St. John’s wort (*Hypericum perforatum*; family Clusiaceae) as toxic to dogs; hypericin can cause photosensitization with ulcerative and exudative dermatitis.
HIGH · poison_control_database · St. John's Wort - Toxic and Non-toxic Plants
The page does not explicitly state the exposure route or whether risk varies by preparation or concentration.