# Horsetail (Equisetum arvense) *Field horsetail, shave-grass, bottle-brush, paddock-pipes, pewterwort; *Cauda equina* of the old pharmacopoeias; *Equisetum arvense* of Linnaeus; the Greek *hippouris* of Dioscorides; in pharmacy *Equiseti herba** **Known today as.** *Equisetum arvense*, the commonest British horsetail, a rush-like plant of cornfields and wet meadows from a creeping rootstock, with no true leaves: its jointed, grooved, hollow stems end at each joint in a toothed sheath. A short, pale fertile stem with a cone appears in early spring and soon withers; the green barren stems that follow carry whorls of slender jointed branches, and these are the medicine. The name, Grieve says, is from Latin *equus*, horse, and *seta*, bristle, for the bristly look of the stems. Kind: Plant > **Caution.** Not where a reduced fluid intake is recommended, as in severe heart or kidney disease, nor for children under twelve, nor in pregnancy or breast-feeding, and not to be applied to the breast while breast-feeding. Fever, painful urination, spasms, or blood in the urine call for a doctor, as do signs of skin infection. LiverTox rates it a probable rare cause of liver injury: oral forms “have been implicated in instances of serum aminotransferase elevations,” though not convincingly in liver injury with jaundice. ## What was it used for? A diuretic and staunching herb. Grieve gives it for dropsy, gravel, and kidney complaints, and the powdered herb as “very effectual in spitting of blood”; the decoction, she says, applied outwardly “will stop the bleeding of wounds and quickly heal them.” Culpeper found it “very powerful to staunch bleeding either inward or outward,” good for fluxes and bloody urine, for ulcers, for the stone, and for “a cough that comes by distillations from the head.” ## What does modern science say? The European Medicines Agency’s herbal committee accepts the herb as a traditional herbal medicine, “exclusively based upon long-standing use,” to increase the amount of urine and so flush the urinary tract, as an adjuvant in minor urinary complaints, and for the supportive treatment of superficial wounds (monograph of 2016). Its assessment report finds 5 to 7.7 per cent silicic acid and silicates and flavonoid glycosides of kaempferol and quercetin, and notes that the fresh and dried plant hold much thiaminase, an enzyme destroyed by heating to 80 C and not found active in the industrial extracts. ## Pharmacognosy and toxicology - **silicic acid**: with silicates, 5 to 7.7 per cent - **kaempferol**: as flavonoid glycosides, with quercetin - **quercetin**: - **thiaminase**: an enzyme abundant in the fresh and dried plant, destroyed by heating to 80 C **Mechanism.** Not established in the sources read for this entry. **Standing.** European Union herbal monograph (2016): traditional use, “exclusively based upon long-standing use,” to flush the urinary tract in minor urinary complaints and for superficial wounds. ## What lore surrounds it? Its silica made it a scourer. One species, *Equisetum hyemale*, Grieve writes, was sold in bunches for polishing metal and imported from Holland, hence Dutch rushes; Gerard knew it for scouring pewter and wooden kitchenware, whence pewterwort, and fletchers and comb-makers polished their work with it, and the dairymaids of the north scoured their milk pails with it long after. Linnaeus reported that in Sweden horses ate some species well while cows lost their teeth on them; the Roman poor are said to have eaten the young shoots, which Grieve calls “neither palatable nor very nutritious.” Giant horsetails of the coal age, she adds, left the fossils called *Calamites*. ## What did the older authorities say? **Dioscorides.** His *hippouris* grows in moist places and ditches, with hollow reddish jointed stalks surrounded by thin rushy leaves and black filaments “similar to the tail of a horse.” Its juice stops nosebleeds; drunk in wine it helps dysentery and brings on urine, and sprinkled on it closes bleeding wounds. **Nicholas Culpeper.** “The herb belongs to Saturn, yet is very harmless,” the smoother kind better than the rough. It “soon solders together the tops of green wounds,” and “cures all ruptures in children.” ## Sources - Grieve, M. *A Modern Herbal*, “Horsetails.” As published on botanical.com. - Culpeper, N. *The Complete Herbal*, “Horsetail.” Project Gutenberg, 49513. - Dioscorides. *De materia medica*, 4-46, in the modern English version of T. A. Osbaldeston and R. P. A. Wood (Johannesburg: Ibidis, 2000), after Goodyer’s translation of 1655. Internet Archive. - European Medicines Agency, Committee on Herbal Medicinal Products. *European Union herbal monograph on Equiseti herba (Horsetail herb)*. EMA/HMPC/278091/2015, 2 February 2016. - European Medicines Agency, Committee on Herbal Medicinal Products. *Assessment report on Equiseti herba*. EMA/HMPC/278089/2015, 2 February 2016. - LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, “Horsetail.” National Institute of Diabetes and Digestive and Kidney Diseases, updated 2022. NCBI Bookshelf. - European Medicines Agency, Committee on Herbal Medicinal Products. *European Union herbal monograph on Equiseti herba (Horsetail herb)*. EMA/HMPC/278091/2015, 2 February 2016. - European Medicines Agency, Committee on Herbal Medicinal Products. *Assessment report on Equiseti herba*. EMA/HMPC/278089/2015, 2 February 2016. - LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, “Horsetail.” National Institute of Diabetes and Digestive and Kidney Diseases, updated 2022. NCBI Bookshelf. --- *Horsetail.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-16. The Thinking Press. https://thethinkingpress.org/materia-medica/horsetail Historical description, not medical advice.