Horsetail

Horsetail (Equisetum arvense) has traditionally been used in Europe as an oral diuretic for the treatment of edema. The German Commission E expert panel has approved horsetail for this indication. Horsetail is also occasionally used for osteoporosis, nephrolithiasis, urinary tract inflammation, and wound healing (topical). These uses have largely been based on anecdote and clinical tradition, rather than scientific evidence.
There is preliminary human evidence supporting the use of horsetail as a diuretic. One poorly designed human trial found horsetail to effectively raise bone density equally to calcium supplements.
In theory (based on mechanism of action), horsetail ingestion in large amounts may cause thiamine deficiency, hypokalemia, or nicotine toxicity. Reported adverse effects include dermatitis.

Synonyms

Bottle brush, cola de caballo, common horsetail, common scouring rush, corncob plant, corn horsetail, Dutch rush, field horsetail, horse willow, horsetail grass, horsetail rush, mokuzoku, mokchok, muzei ( E. hymale ), paddock pipes, pewterwort, prele, pribes des champs, running clubmoss, Schachtelhalm, scouring rush, Shenjincao, shave grass, toadpipe, Wenjing, Zinnkraut.
Crude drugs derived from Equisetum arvense include Wenjing, Jiejiecao, and Bitoucai.
Note: Equisetum arvense should not be confused with members of the genus Laminaria, kelp, or brown alga, for which "horsetail" has been used as a synonym.

Evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Uses based on scientific evidence

Diuresis (increased urine)
Use of horsetail dates to ancient Roman and Greek medicine. The name Equisetum is derived from equus, "horse" and seta, "bristle." Preliminary human and laboratory research suggests that horsetail may increase the amount of urine produced by the body. More studies are needed to determine if horsetail is safe or useful for specific health conditions.
Osteoporosis (weakening of the bones)
Silicon may be beneficial for bone strengthening. Because horsetail contains silicon, it has been suggested as a possible natural treatment for osteoporosis. Preliminary human study reports benefits, but more detailed research is needed before a firm recommendation can be made. People with osteoporosis should speak with a qualified healthcare provider about possible treatment with more proven therapies.

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Antioxidant, antibacterial, antioxidant, astringent, bladder disturbances, bleeding, brittle fingernails, cancer, cosmetics, cystic ulcers, diabetes, dropsy, fever, fluid in the lungs, frostbite, gonorrhea, gout, hair loss, hepatitis, itch, kidney disease, kidney stones, leg swelling, liver protection, malaria, menstrual pain, nosebleeds, prostate inflammation, styptic (to stop bleeding cuts on the skin), Reiter's syndrome, rheumatism, stomach upset, thyroid disorders, tuberculosis, urinary incontinence, urinary tract infection (UTI), urinary tract inflammation, wound healing.

Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.
Standardization
Standardization involves measuring the amount of certain chemicals in products to try to make different preparations similar to each other. It is not always known if the chemicals being measured are the "active" ingredients. There is no widely recognized standardization for horsetail products. Standardization may be difficult, as approximately 25 species of Equisetum exist, and it is often difficult to differentiate between species. In Europe, the silicon content in horsetail may be less than 15%. Some experts recommend that horsetail should be standardized to 10% silicon per dose.
Adults (18 years and older)
Recommended doses for horsetail are based on historical use or expert opinion. There are no reliable studies in humans that show horsetail to be effective or safe at any specific dose.
By Mouth:
Tablets/Capsules: Different doses have been used, starting at 300 milligram capsules taken three times per day, up to 6 grams per day.
Tea: A maximum of 6 cups of tea, containing 1.5 grams of dried stem in one cup of hot water, is a dose that has been used.
Tincture(1:1 in 25% alcohol): 1 to 4 milliliters three times daily has been used.
Applied to the skin:
External wash: A wash prepared by mixing 10 teaspoons of horsetail in cold water and soaking for 10 to 12 hours has been used.
Children (younger than 18 years)
There is not enough scientific information to recommend the use of horsetail in children. Poisonings have been reported in children using horsetail stems as whistles.