Field horsetail for hair and nails (silica): how to use

Field horsetail is mainly sold in Poland with the slogan about hair and nails, based on one argument: no other herb contains as much silica. The content is indeed high. The problem arises one step further, with the question of how much of this silica actually comes from the plant and reaches the body, and what field horsetail is allowed for in the European Union. The answers to both questions are documented, and both are less convenient than product descriptions suggest. We have gathered them together with two safety issues that are usually not mentioned in Polish guides: the species that may be a contaminant in poorly collected raw material, and what the famous warning about vitamin B1 really concerns.

KEY INFORMATION
• The European Union monograph allows field horsetail herb only for rinsing the urinary tract and as an adjunct for superficial wounds, not for hair or nails (EMA monograph, Equiseti herba).
• The herb contains 5-7.7% silicic acid, but only about 10% of that dissolves in water.
• The recommended time of use is 2-4 weeks, not several months; if symptoms persist for more than a week, the monograph advises seeing a doctor.
• Mud horsetail, similar in appearance, contains toxic palustrin and may be a contaminant in raw material collected by unqualified individuals.

What is documented about field horsetail, and what is not?

The European monograph classifies field horsetail herb as a traditional herbal medicinal product and indicates two uses. The oral use involves increasing urine output to rinse the urinary tract, as an adjunct for minor ailments in this area. The external use concerns supporting the treatment of superficial wounds. The column for raw materials with recognized efficacy remains empty.

Among the indications, there are no mentions of hair, nails, skin, or cellulite. This is not an oversight by the regulator. The evaluating report noted the position of the panel of the European Food Safety Authority from 2009, according to which field horsetail has not been sufficiently characterized for the maintenance of skin, hair, or bones (EMA evaluating report, Equisetum arvense L., herba, 2015).

There is a tradition of use in this area, and the report mentions it alongside several other folk applications, from stopping bleeding to baths for rheumatic ailments. However, tradition is a descriptive category, not a proof-based one: the registration of a traditional herbal product does not require efficacy studies, only documented thirty years of use. A review of the pharmacology of the entire genus confirms the same distribution of emphasis, indicating diuretic action as the only confirmed effect in humans (Boeing et al., Evidence-Based Complementary and Alternative Medicine, 2021). If you are interested in this direction, we have gathered it in a text about natural support for kidneys and urinary tract.

How much silicon really passes from horsetail to the body?

Content and bioavailability are two different matters, and with horsetail, they diverge drastically. The herb contains about 5-7.7% silicic acid, which is indeed a high value for a plant. However, only about 10% of that is water-soluble.

Experimental measurement shows this even more sharply. The silicon content in the whole plant is about 5%, while the maximum amount that can be extracted with water is 0.3% of the plant’s mass, with the infusion prepared without boiling. The authors of another study conclude that high silica content simply cannot be extracted by ordinary tea brewing; soaking the raw material and boiling it for several hours significantly increases yield. This is why the monograph recommends preparing the infusion by boiling the herb for 5-15 minutes, rather than pouring boiling water over it for a moment.

The practical conclusion is inconvenient for both popular forms. A homemade infusion extracts a fraction of the silica, and a capsule with declared standardization on silicon dioxide speaks of the content in the powder, not how much of it is absorbed. The percentage declaration on the packaging is therefore information about the raw material, not a promise of the absorbed dose. The evaluating report closes this matter with one sentence: there is no data on absorption, distribution, metabolism, and excretion for this raw material.

Do studies on silicon and hair concern horsetail?

No, they do not. Clinically binding studies linking silicon to hair quality examined ortho-silicic acid stabilized with choline, a substance produced industrially, with a different chemical form than plant silica. This distinction disappears in commercial descriptions, yet it is the basis of the entire argument.

In the first of these trials, 50 women with sun-damaged skin took 10 mg of silicon daily in this form or a placebo for 20 weeks. Skin roughness parameters improved, and the subjective assessment of hair and nail brittleness was significantly lower after 20 weeks than at the start (Barel et al., Archives of Dermatological Research, 2005). The second trial involved 48 women with fine hair, over 9 months, at the same dose. The tensile strength decreased significantly in the placebo group by 10.8%, while in the silicon group, it decreased by only 2.20%, which is not significant. Hair elasticity decreased by 4.52% compared to 11.9% in the placebo group, and the cross-sectional area of the hair increased (Wickett et al., Archives of Dermatological Research, 2007).

Note the direction of this result, as it is sometimes misrepresented. The hair did not become stronger than at the beginning. It deteriorated more slowly than in the placebo group. This is a real observation, but described as a percentage increase in strength becomes untrue, and attributed to field horsetail becomes doubly untrue. Studies on horsetail and nails, which the evaluating report mentions, concerned an external preparation combining extract with a sulfur donor, applied to the nail plate for 28 and 14 days, not oral supplementation.

How long is it allowed to use horsetail and who should avoid it?

The European monograph states that herbal preparations are traditionally used for a period of 2 to 4 weeks. It separately stipulates that if symptoms persist for more than a week during the use of the preparation, one should contact a doctor or pharmacist. This is a completely different time horizon than several-month treatments described in beauty guides.

Contraindications are short and specific. Hypersensitivity to the raw material excludes use. It is also excluded in any condition where fluid intake is recommended to be limited, including severe heart and kidney diseases. For preparations other than teas, the monograph requires ensuring adequate fluid intake. Use in children under 12 years of age is not recommended due to lack of data.

Safety during pregnancy and breastfeeding has not been established, and due to insufficient data, the monograph does not recommend use during this period. External preparations should not be applied to the breast of a nursing woman. There is no data on the impact on fertility. In the drug interaction section, there is an entry about the lack of reports, so widespread warnings about combining horsetail with lithium have no basis in this document. The evaluating report indicates another lead that guides do not mention: in studies of interactions using water extracts, inhibition of CYP2C8 and CYP1A2 enzymes was observed, and this result was recommended to be considered in clinical assessment. Additionally, there are two observations from the literature: caution in individuals with impaired potassium metabolism due to the high content of potassium in horsetail, and possible digestive discomfort with prolonged use.

How does field horsetail differ from mud horsetail?

One is a pharmacopoeial raw material, while the other contains a compound considered toxic. Mud horsetail, a species similar in appearance and growing in similar places, contains palustrin. Veterinary literature has noted that a contamination of about 1% of mud horsetail in hay can cause severe harm to animals.

The evaluating report states the matter directly: contamination of the raw material with mud horsetail and several other species is possible. Therefore, the European Pharmacopoeia provides for identity testing of this herb using thin-layer chromatography, with a specification for the absence of mud horsetail. The recommendation for the patient in this document is unequivocal: only quality-controlled raw material from a pharmacy should be consumed, as contamination is possible when collected by unqualified individuals.

This is why self-collection of horsetail in the meadow is a bad idea, even if species identification seems certain. Substitution within the same genus is invisible to the buyer and does not show up in taste or appearance of the dried herb. Laboratory testing resolves the matter, which home collection does not pass. Our store does not carry field horsetail in any form, so for raw material with confirmed identity, go to a pharmacy.

Where did the issue of thiaminase come from and does it concern every preparation?

Horsetail contains thiaminase, an enzyme that breaks down vitamin B1, and this is a documented fact, but it is usually described without three caveats that the evaluating report gathered, which change the conclusion. First: the enzyme is thermolabile. In the cited study from 1993, it was completely inactivated at 80 degrees Celsius, and the temperature of half-denaturation was about 70 degrees.

The second caveat is even more important. In industrial dry water extracts and in liquid extract with 30% ethanol, thiaminase activity has not been detected at all. The third concerns humans: in traditional European medicinal use, neither brain damage in individuals with thiamine deficiency nor toxic reactions resembling nicotine poisoning have been observed. Descriptions of poisoning come from veterinary medicine, from horses fed hay with horsetail, and these drive warnings prescribed in guides for humans.

The regulator drew a proportional conclusion: for preparations covered by the monograph, i.e., infusions and extracts, no warning was proposed on the packaging, as the enzyme is destroyed by both boiling and ethanol extraction. The question of powdered herb remains open, which undergoes neither process. The Canadian regulator went further and requires manufacturers to demonstrate that products from field horsetail are free from thiaminase activity. Therefore, the recommendation to routinely supplement vitamin B1 with any form of horsetail has no support in the European assessment, and for dried herb for brewing and extracts, it is irrelevant.

Frequently Asked Questions

Does field horsetail work for hair and nails?

There is no evidence that meets regulatory requirements. The European monograph allows the herb only for rinsing the urinary tract and as an adjunct for superficial wounds, and the panel of the European Food Safety Authority concluded in 2009 that the raw material has not been sufficiently characterized for the maintenance of hair, skin, and bones.

How much silica does field horsetail contain and how much is absorbed?

The herb contains 5-7.7% silicic acid, but about 10% of that is water-soluble. In an experimental study, the maximum amount of silicon extracted with water was 0.3% of the plant’s mass when brewed without boiling. The percentage declaration on the packaging describes the raw material, not the absorbed dose.

How long can field horsetail be used?

The European monograph states a period of 2 to 4 weeks as the traditional time of use and requires contacting a doctor if symptoms persist for more than a week during the use of the preparation. Several-month treatments described in beauty guides exceed this document.

Did studies on silicon for hair concern field horsetail?

No. They studied ortho-silicic acid stabilized with choline, a substance with a different chemical form than plant silica. In a trial of 48 women over 9 months, hair in the placebo group weakened by 10.8%, while in the silicon group, it weakened by 2.20% (Wickett et al., 2007). This is a slowing of deterioration, not strengthening.

Can field horsetail be used during pregnancy and breastfeeding?

It is not recommended. Safety has not been established, and due to insufficient data, the European monograph advises against use during pregnancy and breastfeeding. External preparations should not be applied to the breast of a nursing woman. There is no data on the impact on fertility.

Do you need to take vitamin B1 with horsetail?

There is no basis for this with infusions and extracts. Thiaminase from horsetail is thermolabile and its activity has not been detected in industrial water extracts or in ethanol extract. Reports of poisoning come from veterinary medicine; such events have not been observed in humans in traditional European use. The powdered herb remains an open question.

Can field horsetail be collected by oneself?

Better not. It is possible to confuse it with mud horsetail, which contains toxic palustrin, and identification by the appearance of the dried herb is unreliable. The European Pharmacopoeia provides for chromatographic testing of this raw material to confirm the absence of mud horsetail, and the evaluating report recommends using only quality-controlled material.

If you are looking for verifiable ways to work on hair condition, we have prepared separate texts on how hemp oil works on hair and scalp and on whether apple cider vinegar really works on hair.

This article is for informational and educational purposes and does not constitute medical advice. Before starting supplementation, consult your doctor, especially if you are taking medications regularly, are pregnant or breastfeeding, or have chronic illnesses.

Author: Michał Waluk · Published: 2026-07-06 · Updated: 2026-08-16