Scientific Name: Horsetail
Other Names: Bottle-brush, Dutch Rushes, Paddock-pipes, Pewterwort, Scouring Rush, Shave-grass, Toadpipe

Who is this for?

Uses

Note: Horsetail may contain nicotine, which is more likely to cause potentially serious side effects in children than in adults. Therefore, horsetail is not recommended for individuals under the age of 18.

Horsetail contains chemicals that have a mild diuretic action--they promote the loss of water from the body. Taken orally for a few days, at most, horsetail may relieve mild swelling caused by excess water in the body. Historically, it has also been used to treat bladder, kidney, and urinary tract infections, but prescription diuretics ("water pills") and antibiotics are now much more effective for both of these uses.

More recently, horsetail has been studied for its possible usefulness in treating arthritis, osteoporosis, and other conditions of bones and cartilage. Horsetail contains relatively large amounts of silica and smaller amounts of calcium. Both silica and calcium are components of bones, joints, and connective tissues such as tendons and ligaments. It is believed that proteins in body tissues need silica to combine properly. Isolated results from early studies of animals show that horsetail may also have some pain-relieving and anti-inflammatory effects, which could add to its potential as a treatment for arthritis and related conditions. Some case reports relate the use of horsetail to lower incidences of osteoporosis. However, more research--including placebo-controlled studies in humans--needs to be conducted to determine whether or not horsetail may be safe and effective for bone and joint conditions.

Other chemicals in horsetail have an astringent effect that may lessen bleeding and speed healing of minor skin injuries such as cuts and scrapes when it is applied to the skin. An astringent helps shrink and tighten the top layers of skin or mucous membranes, thereby reducing secretions, relieving irritation, and improving tissue firmness. Oil distilled from horsetail has shown some anti-infective effects in laboratory studies. Because it may tighten skin tissue, horsetail is often included in nonprescription "anti-aging" skin care products.

Children under the age of 18 and individuals who are allergic to nicotine should not take horsetail by mouth, because it contains small amounts of nicotine A nicotine-like poisoning reaction has been reported among children who chewed on fresh horsetail stems.

The diuretic effects of oral horsetail may worsen heart disease or kidney conditions by decreasing the levels of potassium in the body. Therefore, individuals with heart problems or kidney disorders should avoid taking horsetail by mouth.

Precautions

The amount of nicotine that could pass from a pregnant woman taking horsetail to a developing fetus or from a breast-feeding woman to an infant is probably too small to be measured. However, the use of horsetail is not recommended during pregnancy or while breast-feeding.

What side effects should I watch for?

Major Side Effects

Cattle and other animals that continually eat large quantities of horsetail may suffer from toxicity similar to nicotine poisoning. Typically, affected animals appear weak--gradually losing muscle control over a period of days or weeks unless they stop eating horsetail. Some animal deaths have been attributed to horsetail poisoning. Although horsetail is not thought to have caused deaths among humans, it has been reported to cause muscular weakness in children who have put the hollow stems into their mouths to use as straws or whistles. The effects of nicotine are more pronounced for children than adults. Therefore, individuals under the age of 18 should not take horsetail.

Horsetail is known to block the absorption of thiamine, one of the B vitamins. If it is taken for more than a few days, a thiamine deficiency is remotely possible. Initial symptoms of thiamine deficiency may include constipation, fatigue, irritability, loss of appetite, memory loss, or sleep disturbances. If prolonged, thiamine deficiency may cause nerve damage.

Less Severe Side Effects

Occasional ases of seborrheic dermatitis--an oozing, scaly, itchy rash--have been reported by individuals taking or handling horsetail.

What interactions should I watch for?

Prescription Drugs

Individuals who take a diuretic drug should talk to a doctor or pharmacist before using horsetail. Diuretics include Dyazide, furosemide, hydrochlorothiazide, and many others.

In addition, diuretics may promote the loss of potassium from the body. Since horsetail's diuretic action may also lead to potassium loss, dangerously low levels of potassium in the blood (also known as hypokalemia) may result if horsetail is taken at the same time as a diuretic. Symptoms of hypokalemia may include:

• Abdominal cramps
• Constipation
• Low blood pressure
• Muscle weakness
• Nausea
• Vomiting
• Hallucinations
• Respiratory failure
• Cardiac arrest

Possible potassium deficiency caused by the diuretic action of horsetail may increase the effects and the risk of side effects from digoxin, a drug used to increase the force and decrease the rate of heartbeats. If horsetail and digoxin are taken together, heartbeats may become too forceful or too slow, possibly causing dangerous changes in heart rhythm. Digoxin's side effects may include changes in vision, drowsiness, heart rhythm changes, nausea, and vomiting.

Non-prescription Drugs

Horsetail may contain small amounts of nicotine. Taking it at the same time as smoking cigarettes or using nicotine replacement products (gum, lozenges, or patches) could result in nicotine overdose. Symptoms of nicotine overdose may include:

• Difficult breathing
• Drooling
• Intense headache
• Loss of muscle control
• Upset stomach

Note: Even small amounts of nicotine may cause a nicotine overdose in children. Because the nicotine content of horsetail may vary widely, children under the age of 18 should not take it by mouth.

Herbal Products

Horsetail may promote the loss of water from the body, possibly decreasing the body's stores of potassium, as well. When horsetail is taken with other potassium-depleting herbals such as licorice, the chances of potassium deficiency increase. Low potassium levels may result in symptoms such as drowsiness, heart rhythm changes, nausea, and vision disturbances.

Potassium depletion may also result if horsetail is taken at the same time as herbal laxatives including:

• Aloe
• Rhamnus cathartica
• Rhamnus frangula
• Rhamnus purshiana
• Senna
• Yellow Dock

If horsetail is taken with other herbal products, such as motherwort or squill, that have effects on the heart, the chance of side effects may increase. Possible side effects include:

• Changes in heart rhythm
• Drowsiness
• Nausea
• Vision disturbances
• Vomiting

Some interactions between herbal products and medications can be more severe than others. The best way for you to avoid harmful interactions is to tell your doctor and/or pharmacist what medications you are currently taking, including any over-the-counter products, vitamins, and herbals. For specific information on how horsetail interacts with drugs, other herbals, and foods and the severity of those interactions, please use our Drug Interactions Checker to check for possible interactions.

Should I take it?

Horsetail is related to the fern family of plants. An ancient plant form believed to be native to Europe, it is now found in most mild, wet climate zones. In parts of eastern Europe, it is grown as a field crop; but it is considered a weed in most farming areas. Especially in damp meadows and pastures, horsetail spreads quickly. If grazing animals eat too much of it, they may have a toxic reaction that can include diarrhea, fever, loss of muscle coordination, weakness, and eventual death.

Horsetail has two kinds of stems--both about a foot tall. The first to appear very early in the spring are yellow or tan reed-like stalks that look much like bamboo. They have thick, hollow stems, no leaves, and a cone-shaped top where spores form. After a few weeks, the first shoots die back and hollow, green stalks bearing thin leaves resembling pine needles appear. These feathery leaves make horsetail plants resemble the brushes used to clean baby bottles--hence one of its common names "bottle-brush". Horsetail plants do not have flowers. Because horsetail stalks contain a high percentage of silica, a sandy mineral, they have been used at various times to scour pots, polish metals, or sand wooden implements. For medicine, the second type of horsetail stems are cut in late summer and dried.

Dosage and Administration

Taking horsetail by mouth is not recommended for individuals under the age of 18 years, due to possible side effects from the small amount of nicotine that horsetail may contain.

Orally, horsetail is available as capsules, tablets, and tincture. All of these oral dosage forms should be taken with a full glass of water. For adults, a typical oral dose of horsetail is 300 mg three times a day. Horsetail tea may be made by soaking up to 2 teaspoons of dried horsetail in about 6 ounces of boiling water for 5 minutes and then straining out the solid particles. Up to three cups of horsetail tea may be consumed per day. No more than 6,000 mg (6 grams) of oral horsetail are recommended to be taken per day and horsetail should not be taken continuously for more than 5 days at a time.

Usually in combination with other herbals and more commonly in Europe than in the United States, topical horsetail products such as creams, lotions, or ointments may be available commercially. In addition, cooled horsetail tea may be applied directly to irritated skin as often as needed. It can also be used as a poultice, which is usually a soft cloth that has been soaked in a medication, possibly heated, and applied to an aching or injured area of skin surface. For a stronger topical solution, 10,000 mg (10 grams) of dried horsetail may be soaked in one quart of boiling water. This solution should not be consumed and it should be applied to the skin only after it has cooled enough to be comfortably warm but not hot. It should be stored out of the reach of children or pets in a tightly capped container that is clearly marked to be used on the skin only. Reportedly, horsetail may be added to bath water to help relieve widespread skin conditions.

Summary

When taken by mouth, horsetail acts as a mild diuretic. It may also have some benefit in treating conditions of the bones and connective tissues. Topically, it is used to treat skin injuries.

Risks

Due to its nicotine content, horsetail should not be taken orally by children under the age of 18, individuals who are allergic to nicotine, or pregnant and breast-feeding women. Individuals with poor kidney function or heart conditions should also avoid the oral use of horsetail.

Side Effects

Symptoms of nicotine-like poisoning have been reported in animals and children who consumed horsetail. Thiamine deficiencies may also have resulted from the oral use of horsetail. Taking, applying, or handling horsetail may result in an itchy rash.

Interactions

Taking horsetail may reduce potassium levels in the body. Low potassium levels can result in muscle weakness and potentially dangerous changes in heart rhythm. The chance of potassium deficiency is increased if horsetail is taken at the same time as drugs and herbal products that promote water loss ("water pills" and some laxatives.) If horsetail is taken with digoxin or herbs that affect the force and timing of heartbeats, the risk of side effects may be increased.

Last Revised October 12, 2007

References

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Last Revised October 12, 2007

Note: The above information is not intended to replace the advice of your physician, pharmacist, or other healthcare professional. It is not meant to indicate that the use of the product is safe, appropriate, or effective for you.

In general, herbal products are not subject to review or approval by the U.S. Food and Drug Administration (FDA). They are not required to be standardized, meaning that the amounts of active ingredients or contaminants they contain may vary between brands or between different batches of the same brand. Not all of the risks, side effects, or interactions associated with the use of herbal products are known because few reliable studies of their use in humans have been done.

This information is provided for your education only. Please share this information with your healthcare provider and be sure that you talk to your doctor and pharmacist about all the prescription and non-prescription medicines you take before you begin to use any herbal product.

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