Wood horsetail Toxic?

Updated 2026-03-06| 3 min read| 4,413 found this helpful

Equisetum sylvaticum L.

All parts of the plant are toxic, and alkaloid content remains stable after drying, so contaminated hay poses equal risk to fresh plant material

Toxicity is driven by piperidine alkaloids, primarily palustrin, that cause vitamin B1 deficiency specifically in equine species

Early vitamin B1 administration is the only curative treatment for affected horses, paired with decontamination and symptomatic care

FAQ

Is Wood horsetail toxic to Humans?

No specific exposure data available; monitor for gastrointestinal distress, fatigue and neurological changes if ingestion is suspected (Low)

Is Wood horsetail toxic to Cats?

No species-specific symptom data available; monitor for appetite loss, diarrhea and coordination changes if ingestion is suspected (Low)

Is Wood horsetail toxic to Dogs?

No species-specific symptom data available; monitor for appetite loss, diarrhea and coordination changes if ingestion is suspected (Low)

Is Wood horsetail toxic to Horses?

Causes 'staggers disease' from vitamin B1 deficiency, with symptoms including appetite loss, weight loss, unsteadiness, progressive incoordination, saw-horse stance, hindlimb paralysis, recumbency, blindness, post-exercise muscle fasciculations, opisthotonus, central seizures and fatal outcomes in severe cases (High)

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Toxicity Details

Humans

Low

No specific exposure data available; monitor for gastrointestinal distress, fatigue and neurological changes if ingestion is suspected

Cats

Low

No species-specific symptom data available; monitor for appetite loss, diarrhea and coordination changes if ingestion is suspected

Dogs

Low

No species-specific symptom data available; monitor for appetite loss, diarrhea and coordination changes if ingestion is suspected

Horses

High

Toxicity Snapshot

Toxic PartsEntire plant, both above-ground and below-ground tissues

Exposure RouteIngestion (primary exposure route for grazing livestock and accidental human/companion animal consumption)

Toxic CompoundsPiperidine alkaloids; Palustrin; Palustridiene; N5-Formylpalustrin (Palustridin); N5-Acetylpalustrin; N5-Formylpalustridiene

First Aid & Prevention

First 30 Minutes

• Remove all remaining plant material from the affected subject's access and mouth to stop further ingestion
• Administer activated charcoal if ingestion occurred within the past 2 hours to reduce alkaloid absorption
• Contact a veterinarian or poison control center immediately for species-specific guidance

Contact Vet Immediately

• Any confirmed or suspected ingestion of wood horsetail by horses or other grazing livestock
• Observation of clinical symptoms including appetite loss, incoordination, diarrhea or neurological changes
• Confirmation that hay or forage fed to animals is contaminated with Equisetum species plant material

Prevention

• Inspect grazing pastures regularly to remove wild horsetail growth before allowing livestock access
• Avoid feeding hay or forage contaminated with any Equisetum species, as alkaloids remain toxic when dried
• Store livestock feed and forage in areas free of wild horsetail growth to prevent accidental contamination

Treatment & Prognosis

• Perform decontamination procedures including gastric lavage and activated charcoal administration as appropriate for time since ingestion
• Administer vitamin B1 as directed: 100-200mg orally twice daily on day 1, then once daily for 7-14 days
• Provide supportive symptomatic care including fluid therapy for diarrhea, seizure control and nutritional support as needed

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Professional Toxicology

Scientific NameEquisetum sylvaticum L.

AliasesWald-Schachtelhalm (German common name)、Prêle des bois (French common name)、Equiseto selvatico (Italian common name)

Toxicity Grade

HumansLow

CatsLow

DogsLow

HorsesHigh

Target Organs

Gastrointestinal tractCentral nervous systemMusculoskeletal systemOcular tissue

Mechanism of Action

• Piperidine alkaloids in the plant inhibit thiamine (vitamin B1) uptake and utilization, leading to acute thiamine deficiency in equines

• Total alkaloid content remains stable after drying, so contaminated dry forage poses the same risk as fresh plant material

• Above-ground plant tissues have higher alkaloid concentrations, with levels rising from spring to the end of the growing season

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Pony: Feeding trials with 5% marsh horsetail (related Equisetum species) in feed resulted in development of characteristic thiamine deficiency staggers disease symptoms consistent with equine toxicity presentations

Cattle: Exposure may cause appetite loss, weight loss, reduced milk production, diarrhea and neurological disorders as reported for related toxic Equisetum species

Confusion Risk

The following plants look similar and may be confused:

Other horsetail species Equisetum spp.

All Equisetum species have very similar visual characteristics including jointed hollow stems and brush-like foliage. Toxicity levels vary across species, so all wild horsetail growth should be treated as potentially toxic to livestock.

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Related Toxic Plants

Low to moderate toxicity

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Data Sources

1. CliniTox (Universität Zürich)

This information is for reference only and does not constitute medical advice. If ingestion or poisoning is suspected, seek medical or veterinary attention immediately.

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