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Botanical Description & Habitat

Horsetail (Equisetum hyemale) is a rush which grows in damp soils both in Europe and America.

When in bloom it takes on the appearance of a horse's tail. Otherwise it is merely a stalk.

Historical Properties & Uses

Horsetail, or shavegrass, has proven antibiotic properties; it is popular as a mouthwash and gargle to prevent infectious disease. Horsetail is a rich source of beneficial trace elements and minerals. Horsetail is high content of silicic acid has been implicated in the successful treatment of tuberculosis and other infectious diseases, although its mechanism of action is unknown.

Horsetail has mild anti-inflammatory and hypotensive properties. It is often used to treat kidney disease, but there is no direct experimental support for this practice. Use of the herb as a diuretic has received only occasional support in experimental studies and routine screenings.

This herb has approval status by the German Commission E internally for edema and externally as a supportive treatment for slow-healing wounds.


Blumenthal, M (Ed.): The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. American Botanical Council. Austin, TX. 1998.

Method of Action

Horsetail has antibiotic properties
Several studies have demonstrated horse tail's antibiotic properties, and shown it to have some antitubercular effect. Among the organisms it inhibited were Staphylococcus aureus, Streptococcus pyogenes, and certain mycobacteria.

Horsetail has anti-inflammatory action
Horsetail has moderate anti-inflammatory activity.

Horsetail may be hypotensive
Horse tail is part of a hypotensive suppository with proven effectiveness. Other herbs in the blend are the garlic plant, mistletoe, milfoil, and amylocaine.

Horsetail is a mild diuretic
Horsetail can increase diuresis from 68% to 196% in animals. Some investigators, however, have failed to find any diuretic effect at all. It may be the herb's effect is due to organic, alcohol soluble substances (mainly flavone glycosides and saponins) partially destroyed during drying or other processing.

Horsetail is a rich source of minerals
Due to its rich mineral content up to 10% silica, horsetail builds up the blood of laboratory animals and human patients.

The silicic acid (soluble SiO2) content of horsetail is primarily responsible for clinically observed healing effects during infectious diseases, especially in certain forms of tuberculosis. There is some dispute, however, about just how much silicic acid is present in the herb, with estimates ranging from less than 1% to as high as 7%-8%. The herb is often used as a silver polish, and is often called scouring rush, argues for the higher content.

Drug Interactions & Precautions

Known Interactions
Since horsetail's diuretic action increases the renal excretion of sodium and chloride, this herb may potentiate the hyperglycemic and hyperuricemic effects of glucose-elevating agents.

Diuretics such as this may also potentiate the action of antihypertensive, ganglionic or peripheral adrenergic blocking drugs, tubocurarine and, to a lesser degree, norepinephrine. It should also be noted the effects of dopamine and diuretic agents are additive.

Possible Interactions
When taken in conjunction with corticotropin (ACTH) or corticosteroids, the diuretic horsetail is more prone to produce hypokalemia. If this strong diuretic being used, an initial dose of the antihypertensive captopril may cause a severe drop in blood pressure within three hours.

The use of diuretics may require dosage adjustments of antidiabetic drugs. The diuretic action of horsetail may reduce renal clearance of lithium. In addition, the nicotinic acid content of the herb may antagonize the effects of heparin.

Horsetail's strong diuretic action may produce digitalis toxicity if digitalis glycosides are being used. In conjunction with aminoglycoside antibiotics, it may also produce ototoxicity; combined with alcohol, narcotics or barbiturates, it may produce orthostatic hypotension.

Strong diuretics such as horsetail, in conjunction with indomethacin, may produce natriuretic effects. The herb may also enhance the nephrotoxicity of cephaloridine.

Prolonged use of diuretics such as horsetail may affect certain laboratory test results, such as electrolytes (especially potassium and sodium), blood urea nitrogen (BUN), uric acid, glucose, and protein bound iodine (PBI).

Safety Factors & Toxicity

Herbalists agree that large doses of horsetail can be poisonous.

Livestock feeding on horsetail have become intoxicated, then paralyzed; death may follow.

The presence of nicotine in the herb, at 0.0001%, should not pose any hazard to humans. Livestock poisoning is probably due not to nicotine, but to the weakly hemolytic saponins, as well as to many other alkaloids besides nicotine.

The FDA classify horsetail as an herb of undefined safety.

This herb has approval status by the German Commission E.


Blumenthal, M (Ed.): The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. American Botanical Council. Austin, TX. 1998.

Preparation & Administration

Three times a day

Dried herb
1-4 grams

made from 1 tsp dried herb

Fluid extract
1:1 in 25% alcohol, 1-4 ml

This herb has approval status by the German Commission E.

Recommended daily dosages in Germany are as follows:

Internal use: 6 g of the herb.

External use: 10 g per liter of water.


Blumenthal, M (Ed.): The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. American Botanical Council. Austin, TX. 1998.

Note: This Herbal Preparation information is a summary of data from books and articles by various authors. It is not intended to replace the advice or attention of health care professionals.


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Equisetum hyemale

Horsetail 2.

? Southwest School of Botanical Medicine