Horsetail
Equisetum arvense L.
Horsetail (Equisetum arvense) is an ancient, non-flowering perennial fern relative with hollow, jointed, bamboo-like stems that are notably rich in silica, giving them a rough, gritty texture historically used for scouring pots.
Last reviewed August 8, 2026
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Is Horsetail safe to use?
IDENTIFICATION WARNING: only Equisetum arvense (field horsetail) is used medicinally. A related species, Equisetum palustre (marsh horsetail), contains a genuinely toxic alkaloid and has caused livestock poisoning — the two can look similar, so never wildcraft horsetail yourself; use a reliably sourced product. Field horsetail itself contains small amounts of an enzyme called thiaminase, which can deplete vitamin B1 (thiamine) with prolonged use — the EMA recommends no more than 4 weeks of continuous use, and long-term daily use isn't advised without medical supervision. It also contains trace nicotine, so it isn't recommended for young children, and topical use has been linked to contact dermatitis in sensitive individuals. Avoid during pregnancy and breastfeeding. May have mild blood-sugar-lowering and diuretic effects — use caution alongside diabetes medications, diuretics, digoxin, or lithium, and monitor electrolytes with prolonged use. Cross-reactivity with carrot allergy has been reported.
This is educational information, not medical advice. See our full Disclaimer before use.
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Used in rituals & traditions
The symbolic and spiritual side of Horsetail is kept in the Cauldron:
- Planetary & elemental correspondence
- Folklore & spiritual associations