Horsetail is a popular fern that has been used as an herbal remedy since the times of the Greek and Roman Empires (1).

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.

Field or common horsetail (Equisetum arvense) is a perennial fern that belongs to the genus Equisetaceae (2, 3).

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 (1, 3).

The plant contains numerous beneficial compounds that confer it multiple health-promoting effects. Of these, antioxidants and silica stand out (1, 3).

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 (2, 3).

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.

Summary

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 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 (1, 4).

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 (5).

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 (1, 4).

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 (5, 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 (7).

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 (8).

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 (9).

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 (10, 11).

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 (12, 13).

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 (14, 15, 16).

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 (18, 19).

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 (20, 21).
  • Antimicrobial activity. Horsetail essential oil seems to have potent activity against bacteria and fungi, including Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Candida albicans (3, 22).
  • Antioxidant activity. Research shows that horsetail is rich in phenolic compounds, a group of powerful antioxidants that inhibit oxidative damage to cellular membranes (3, 23, 24).
  • Antidiabetic effect. Animal and test-tube studies suggest that horsetail extract may help lower blood sugar levels and regenerate damaged pancreatic tissue (25, 26).
Summary

Horsetail has multiple potential health benefits, including improved bone, skin, hair, and nail health.

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 (2).

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 (8).

However, an appropriate dose has yet to be determined by current scientific evidence.

Summary

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.

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 (27).

As for horsetail’s side effects, its use may cause drug-herb interactions when consumed alongside antiretroviral drugs prescribed for HIV treatment (28).

Additionally, the plant contains nicotine. Thus you should avoid it if you have a nicotine allergy or want to quit smoking (29).

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 (30).

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 (31).

Summary

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.

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.