Horsetail is derived from huge, tree-like plants that thrived 400 million years ago during the Paleozoic era. A close relative of the fern, horsetail is a nonflowering weed found throughout parts of Europe, Asia, the Middle East, and North America. The plant is a perennial (returns each year) with hollow stems and shoots that look like asparagus at first. As the plant dries, silica crystals that form in the stems and branches look like feathery tails and give the plant a scratching effect. That accounts for its historic use in polishing metal, particularly pewter.
The aboveground parts of horsetail (fresh or dried) are used for medicinal purposes.
Medicinal Uses and Indications
Horsetail has traditionally been used as a diuretic (helps rid the body of excess fluid by increasing urine output). One study examined the use of horsetail by people who had a history of uric acid kidney stones. The people who took horsetail experienced an increase in diuresis (urine output). Other studies suggest horsetail has antioxidant properties and may inhibit cancer cell growth.
Horsetail has been suggested as a treatment for osteoporosis (thinning bone), because it contains silicon, a mineral needed for bone health. In one study, 122 Italian women took horsetail dry extract or Osteosil calcium 270 mg twice daily (a horsetail/calcium combination used in Italy for osteoporosis and fractures). Both groups who took horsetail experienced improved bone density, however the study was poorly designed. More research is needed to determine whether horsetail has any effect on bone density.
Horsetail is sometimes suggested for the following conditions, although scientific evidence is lacking:
- Kidney stones
- Urinary tract infections
- Brittle nails
- Minor wounds and burns (applied topically; you should never apply herbal supplements to open wounds).
Horsetail is available in the following forms:
- Dried herb
- Liquid preparations
Horsetail preparations should be stored in sealed containers to ensure protection from light.
How to Take It
Because horsetail contains traces of nicotine, it is not recommended for young children.
- Capsule: use a standardized dose that contains 10 to 15% silica
- Herbal infusion (tea): 2 to 3 tsp., 3 times daily. Pour hot water onto herb and steep for 5 to 10 minutes. Drink as directed.
- Tincture (1:5): Speak to a physician for the proper dose for your condition
- External (compresses): 10 g of herb per 1 liter water daily
Be sure to drink enough fluids when taking horsetail preparations by mouth.
The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, contain components that can trigger side effects and interact with other herbs, supplements, or medications. For these reasons, you should take herbs with care, under the supervision of a qualified health care provider trained in the field of botanical medicine.
Horsetail remedies prepared from Equisetum arvense are generally considered safe when used properly. Another species of horsetail, however, called Equisetum palustre is poisonous to horses. To be safe, never take that form of horsetail. Be sure to buy products made by an established company with a good reputation. When possible, select products with guaranteed potency or standardized extracts.
Prolonged use of even the safe form of horsetail (E. arvense) is also not advised.
Taking horsetail by mouth may cause levels of vitamin B1 (thiamin) in the body to drop. If you take horsetail on a regular basis, you should also take a quality multivitamin or at least a B complex supplement daily.
People with heart or kidney disorders, diabetes, or gout should not use horsetail.
DO NOT drink alcohol regularly while taking horsetail because horsetail may cause levels of thiamin to drop.
Horsetail may flush potassium out of the body so people who are at risk for low potassium levels should not take Horsetail.
Women who are pregnant or breastfeeding should not take horsetail.
The effects of horsetail may enhance the effects of certain medications. For this reason, people taking prescription medications should not take horsetail without first consulting a health care provider.
Alcohol: People who are chronic drinkers may have low levels of vitamin B1 (thiamin). Because horsetail can also cause low levels of thiamin, you should not take horsetail if you drink heavily.
Nicotine patches or gum: Horsetail contains some nicotine, and should not be used if you are also using nicotine replacement patches or chewing gum.
Digoxin (Lanoxin): Horsetail may cause low levels of potassium (hypokalemia) in the body. People with heart arrhythmias and those taking digoxin should not use horsetail.
Diuretics (water pills): Horsetail may have weak diuretic properties, meaning it helps rid the body of excess fluid. People who take diuretics should not take horsetail due to the risk of dehydration or low potassium (hypokalemia).
Lithium: By interfering with the body's ability to eliminate Lithium, taking Horsetail with Lithium may result in a dangerous build up of Lithium in the body.
Blumenthal M, Goldberg A, Brinckmann J, eds. Herbal Medicine: Expanded Commission E Monographs. Newton, MA: Integrative Medicine Communications; 2000:208-211.
Bradley P, ed. British Herbal Compendium. Vol. I. Dorset (Great Britain): British Herbal Medicine Association; 1992:92-94.
Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical; 1998:85.
Cetojevic-Simin DD. Antioxidative and antiproliferative activities of different horsetail (Equisetum arvense L.) extracts. J Med Food. 2010;13(2):452-9.
Corletto F. [Female climacteric osteoporosis therapy with titrated horsetail (Equisetum arvense) extract plus calcium (osteosil calcium): randomized double blind study]. Miner Ortoped Traumatol. 1999;50:201-206.
D'Agostino M, Dini A, Pizza C, et al. Sterols from Equisetum arvense. Boll Soc Ital Biol Sper. 1984;60(12):2241-2245.
Do Monte FH, dos Santos JG Jr, Russi M, et al. Antinociceptive and anti-inflammatory properties of the hydroalcoholic extract of stems from Equisetum arvense L. in mice. Pharmacol Res. 2004;49:239-43.
Dos Santos JG Jr, Blanco MM, Do Monte FH, et al. Sedative and anticonvulsant effects of hydroalcoholic extract of Equisetum arvense. Fitoterapia. 2005;76:508-13.
Foster S, Tyler VE. Tyler's Honest Herbal. 4th ed. New York, NY: The Haworth Herbal Press; 1999:219-220.
Gibelli C. The hemostatic action of Equisetum. Arch Intern Pharmacodynam. 1931;41:419-429.
Graefe EU, Veit M. Urinary metabolites of flavonoids and hydroxycinnamic acids in humans after application of a crude extract from Equisetum arvense. Phytomedicine. 1999;6(4):239-246.
Henderson JA, Evans EV, McIntosh RA. The antithiamine action of Equisetum. J Amer Vet Med Assoc. 1952;120:375-378.
LaValle JB, Krinsky DL, Hawkins EB, et al. Natural Therapeutics Pocket Guide. Hudson, OH: LexiComp; 2000:459-460.
Maeda H, Miyamoto K, Sano T. Occurrence of dermatitis in rats fed a cholesterol diet containing field horsetail (Equisetum arvense L.). J Nutr Sci Vitaminol (Tokyo). 1997;43(5):553-563.
Mimica-Dukic N, Simin N, Cvejic J, Jovin E, Orcic D, Bozin B. Phenolic compounds in field horsetail (Equisetum arvense L.) as natural antioxidants. Molecules. 2008 Jul 17;13(7):1455-64.
Nitta A, Yoshida S, Tagaeto T. A comparative study of crude drugs in Southeast Asia. X. Crude drugs derived from Equisetum species. Chem Pharm Bull (Tokyo). 1977;25(5):1135-1139.
Perez Gutierrez RM, Laguna GY, Walkowski A. Diuretic activity of Mexican equisetum. J Ethnopharmacol. 1985;14(2-3):269-272.
Safiyeh S, Fathallah FB, Vahid N, Hossine N, Habib SS. Antidiabetic effect of Equisetum arvense L. (Equisetaceae) in streptozotocin-induced diabetes in male rats. Pak J Biol Sci. 2007 May 15;10(10):1661-6.
Sudan BJ. Seborrhoeic dermatitis induced by nicotine of horsetails (Equisetum arvense L.). Contact Dermatitis. 1985;13(3):201-202.
Tiktinskii OL, Bablumian IA. [Therapeutic action of Java tea and field horsetail in uric acid diathesis]. Urol Nefrol (Mosk). 1983;3(1):47-50.
Wright CI, Van-Buren L, Kroner CI, Koning MM. Herbal medicines as diuretics: a review of the scientific evidence. J Ethnopharmacol. 2007 Oct 8;114(1):1-31.