Is Horsetail Toxic to Cats?
Also known as: Scouring Rush, Snake Grass, Field Horsetail, Equisetum arvense · Equisetum arvense
What makes it toxic
Thiaminase, an enzyme that destroys vitamin B1 (thiamine), plus silicates that irritate the gut. The B1 depletion matters with repeated ingestion.
Warning signs to watch for
Vomiting and diarrhea after a single meal; with chronic grazing, weight loss, weakness and wobbliness from thiamine deficiency.
What to do if your cat eats it
Remove access and monitor after a single meal. If your cat has eaten horsetail repeatedly, see your vet for a thiamine check — deficiency is correctable if caught.
Common questions
Horsetail is sold as an herbal supplement — is it then safe?
No. Supplement products are prepared to limit thiaminase activity; the raw plant carries it in full. Never offer the fresh plant to pets.
Where is my cat likely to find horsetail?
Damp ditches, pond edges and disturbed soil. It spreads aggressively, so gardeners often battle it — keep cats away while clearing it.
More plants checked for cats
This page is general educational information, not a substitute for professional veterinary advice. Every pet is different — if your animal ate something concerning, contact your veterinarian or a pet poison hotline right away. Checking what your pet can eat? Visit our sister site SafeOrToxic.