Horsetail: Benefits, Uses, and Side Effects
Written by Ariane Lang, BSc, MBA on May 28, 2020 — Medically reviewed by Miho Hatanaka, RDN, L.D.
Horsetail is a popular fern that has been used as an herbal remedy since the times of the Greek and Roman Empires (1Trusted Source).
It’s believed to have multiple medicinal properties and is mostly used to improve skin, hair, and bone health.
This article explores horsetail, including its benefits, uses, and downsides.
What is horsetail?
Field or common horsetail (Equisetum arvense) is a perennial fern that belongs to the genus Equisetaceae (2Trusted Source, 3Trusted Source).
It grows wildly in Northern Europe and America, as well as in other moist places with temperate climates. It has a long, green, and densely branched stem that grows from spring to fall (1Trusted Source, 3Trusted Source).
The plant contains numerous beneficial compounds that confer it multiple health-promoting effects. Of these, antioxidants and silica stand out (1Trusted Source, 3Trusted Source).
Antioxidants are molecules that fight free radicals in your body to prevent cell damage. Meanwhile, silica is a compound comprised of silicon and oxygen. It’s believed to be responsible for horsetail’s potential benefits for skin, nails, hair, and bones (2Trusted Source, 3Trusted Source).
Horsetail is mostly consumed in the form of tea, which is made by steeping the dried herb in hot water, though it’s also available in capsule and tincture form.
Horsetail is a fern that contains many beneficial compounds, notably antioxidants and silica. It’s found in the form of tea, tinctures, and capsules.
Horsetail’s potential benefits
Horsetail has been used for thousands of years as an herbal remedy, and current scientific evidence supports most of its potential benefits.
Supports bone health
Research suggests that horsetail may aid bone healing.
Through bone metabolism, bone cells called osteoclasts and osteoblasts continuously remodel your bones to avoid imbalances that could cause brittle bones. Osteoblasts handle bone synthesis, while osteoclasts break down bone through resorption.
Test-tube studies show that horsetail may inhibit osteoclasts and stimulate osteoblasts. This suggests that it’s useful for bone diseases like osteoporosis, which is characterized by overly active osteoclasts that result in fragile bones (1Trusted Source, 4Trusted Source).
Similar results were seen in a rat study that determined that a daily dose of 55 mg of horsetail extract per pound (120 mg per kg) of body weight significantly improved bone density, compared with a control group (5Trusted Source).
Researchers believe that horsetail’s bone-remodeling effect is mostly due to its high silica content. In fact, up to 25% of its dry weight is silica. No other plant boasts as high of a concentration of this mineral (1Trusted Source, 4Trusted Source).
Silica, which is also present in bones, improves the formation, density, and consistency of bone and cartilage tissue by enhancing collagen synthesis and improving the absorption and use of calcium (5Trusted Source, 6).
Acts as a natural diuretic
Diuretics are substances that increase the excretion of urine from your body. Horsetail’s diuretic effect is one of this fern’s most popularly sought after properties in folk medicine (7Trusted Source).
One study in 36 healthy men determined that taking a daily dose of 900 mg of dried horsetail extract in capsule form had a more potent diuretic effect than that of a classic diuretic drug. This was attributed to the plant’s high antioxidant and mineral salt concentrations (8Trusted Source).
However, while these results are promising, current research is limited.
Promotes wound healing and nail health
The topical application of horsetail ointment appears to promote wound healing.
One 10-day study in 108 postpartum women who had undergone an episiotomy during labor — a surgical cut to facilitate childbirth — showed that applying an ointment containing 3% horsetail extract promoted wound healing and helped relieve pain (9Trusted Source).
The study also determined that wound redness, swelling, and discharge improved significantly compared with a control group. Scientists attributed these positive effects to the plant’s silica content.
In rat studies, those treated with ointments containing 5% and 10% horsetail extract showed a wound closure ratio of 95–99%, as well as greater skin regeneration, compared with control groups (10Trusted Source, 11Trusted Source).
Additionally, horsetail extract may be used in nail polish for the management of nail psoriasis — a skin condition that causes nail deformities.
One study determined that using a nail lacquer comprised of a mixture of horsetail extract and other nail-hardening agents decreased signs of nail psoriasis (12Trusted Source, 13Trusted Source).
Yet, research on the direct effect of horsetail on wound healing and nail health is needed to verify these benefits.
Promotes hair growth
Research suggests that horsetail may also benefit your hair, likely thanks to its silicon and antioxidant contents.
First, antioxidants help reduce micro-inflammation and the aging of hair fibers caused by free radicals. Second, a higher silicon content in hair fibers results in a lower rate of hair loss, as well as increased brightness (14Trusted Source, 15Trusted Source, 16Trusted Source).
For example, a 3-month study in women with self-perceived hair thinning determined that taking two daily capsules containing dried horsetail and other ingredients increased hair growth and strength, compared with a control group (17).
Similar results were obtained in other studies that also tested the effect of different blends containing horsetail-derived silica (18Trusted Source, 19Trusted Source).
However, as most studies focus on a mixture of multiple hair growth compounds, research on the effects of horsetail alone is still limited.
Other potential benefits
Horsetail is known for providing many other potential benefits, including:
Anti-inflammatory activity. Test-tube studies show that horsetail extract may inhibit lymphocytes, the main type of defense cells involved in inflammatory immune diseases (20Trusted Source, 21Trusted Source).
Antimicrobial activity. Horsetail essential oil seems to have potent activity against bacteria and fungi, including Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Candida albicans (3Trusted Source, 22Trusted Source).
Antioxidant activity. Research shows that horsetail is rich in phenolic compounds, a group of powerful antioxidants that inhibit oxidative damage to cellular membranes (3Trusted Source, 23Trusted Source, 24Trusted Source).
Antidiabetic effect. Animal and test-tube studies suggest that horsetail extract may help lower blood sugar levels and regenerate damaged pancreatic tissue (25Trusted Source, 26Trusted Source).
Horsetail has multiple potential health benefits, including improved bone, skin, hair, and nail health.
Uses and dosage
Most horsetail products available are marketed as skin, hair, and nail remedies. Nevertheless, you may also find products claimed to manage urinary and kidney conditions (2Trusted Source).
As for its dosage, one human study suggests that taking 900 mg of horsetail extract capsules — the maximum recommended daily dose for dry extracts per the European Medicines Agency (EMA) — for 4 days may produce a diuretic effect (8Trusted Source).
However, an appropriate dose has yet to be determined by current scientific evidence.
Horsetail is mostly used as a skin, hair, nail, and urinary remedy. A dose of 900 mg daily for 4 days may have a diuretic effect, but overall, an appropriate dose has yet to be determined.
Side effects and precautions
As with most herbal supplements, horsetail is not approved by the Food and Drug Administration (FDA) and should be avoided by pregnant and breastfeeding women.
While research in rats suggests that it’s not toxic, human studies are needed (27Trusted Source).
As for horsetail’s side effects, its use may cause drug-herb interactions when consumed alongside antiretroviral drugs prescribed for HIV treatment (28Trusted Source).
Additionally, the plant contains nicotine. Thus you should avoid it if you have a nicotine allergy or want to quit smoking (29Trusted Source).
What’s more, there’s one case of a 56-year-old woman who presented horsetail-tea-induced pancreatitis, or inflammation of the pancreas. Her symptoms ceased when she stopped drinking the tea (30Trusted Source).
Lastly, horsetail has a reported thiaminase activity. Thiaminase is an enzyme that breaks down thiamine, or vitamin B1.
Thus, long-term horsetail intake, or its intake by those with low thiamine levels — such as people with alcohol abuse disorder, may lead to vitamin B1 deficiencies (31Trusted Source).
Given that horsetail is an herbal remedy, it’s not approved by the FDA. Pregnant and breastfeeding women, people with low vitamin B1 levels, and those who take antiretroviral drugs should avoid consuming it.
The bottom line
Horsetail has been utilized as an herbal remedy for centuries.
It’s mostly used for skin, hair, nail, and urinary conditions, and it may be consumed in the form of tea, capsules, and tinctures.
However, it’s not approved by the FDA and should be avoided by pregnant and breastfeeding women, people with low vitamin B1 levels, and those who take antiretroviral drugs.
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