Is Field Horsetail Toxic to Dogs and Cats? (2026)
Equisetum arvense
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Quick facts
| Toxic to dogs | Yes |
|---|---|
| Toxic to cats | No |
| Toxic to horses | Yes |
| Toxic component | Thiaminase (destroys vitamin B1) |
| Onset of symptoms | Develops over weeks of continuous grazing in horses — not a single-exposure risk |
| Indoor / outdoor | outdoor |
If your pet ate this plant
Both lines are staffed 24/7. A consultation fee applies to each. Do not wait for symptoms to appear before calling.
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Symptoms in dogs
- Mild GI upset
Symptoms in horses
- Weight loss
- Incoordination
- Weakness with prolonged grazing
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What to do
Primarily a chronic grazing-exposure hazard for horses via thiamine deficiency; a single incidental taste by a dog is a low concern.
Toxic component and mechanism
The toxic component in Field Horsetail is thiaminase (destroys vitamin b1).
What makes this plant different
Field Horsetail is a thiaminase-containing plant that primarily threatens horses through prolonged grazing exposure, causing a vitamin B1 deficiency rather than a direct chemical poisoning — the same broad mechanism as Bracken Fern.
Plant identification
- Scientific name
- Equisetum arvense
- Family
- Equisetaceae
- Also known as
- Field Horsetail, Scouring rush, Common horsetail, Western horsetail
- Typically found
- outdoor
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Last verified: July 2, 2026 · Cross-referenced with ASPCA Animal Poison Control