How does horsetail extract support hair growth — is it the silica, the antioxidants, or both?

Horsetail (Equisetum arvense) has been part of traditional remedies for centuries, particularly in Europe and Asia, where it was valued for its supposed effects on bones, nails, and hair. Today, it often appears in the marketing of dietary supplements that claim to promote hair growth and thickness. The main arguments usually revolve around two factors: its silica (silicon dioxide) content and its antioxidants. But when we examine the evidence, we need to ask: is horsetail truly effective, and if so, which of these components are responsible?

Hair is largely made of keratin, a fibrous protein that requires strong structural support to resist damage. Silica, a mineral compound of silicon and oxygen, has been proposed as one of the elements that reinforce keratin-based tissues. The reasoning is that silica helps collagen synthesis, which in turn may strengthen the connective tissues that anchor the hair follicle. If the follicle is structurally supported, hair may resist breakage and thinning.

Evidence for this idea is limited. In a randomized, double-blind, placebo-controlled trial, 50 women with sun-damaged skin took 10 mg of silicon a day (as choline-stabilized orthosilicic acid) or a placebo for 20 weeks. In the silicon group, the women's own ratings of hair and nail brittleness were lower after 20 weeks than at the start (Barel et al., 2005). A second trial gave the same compound to 48 women with fine hair for nine months. It reported that hair elasticity declined less than with placebo, and that hair cross-section increased from baseline in the silicon group but not in the placebo group (Wickett et al., 2007). The limitation is important: both studies used a purified silicon compound, not horsetail extract, so they do not show that horsetail supplements have the same effect.

Antioxidants: can they protect follicles against stress?

Hair follicles are highly sensitive to oxidative stress. Oxidative stress refers to the damage caused when free radicals — unstable molecules that react with proteins, lipids, and DNA — accumulate faster than the body can neutralize them. This type of stress has been linked to hair follicle aging, miniaturization, and even premature graying. Horsetail is rich in antioxidants such as phenolic acids and flavonoids, which theoretically counter this damage.

One study by Cetojević-Simin et al. (2010) examined the antioxidant and antiproliferative activities of horsetail extracts in the laboratory. In chemical test systems (sunflower oil and lipid vesicles), the extracts suppressed the formation of lipid free radicals; the only cells tested were cancer cell lines, used to measure growth inhibition. This was an in vitro study, done outside the body, and no hair or skin cells were tested. While it shows that horsetail has antioxidant activity, we cannot conclude that the same effect would happen in human hair follicles in real-world conditions.

Hair loss is rarely explained by one single factor. It usually involves a mix of genetics, hormonal influence, follicle sensitivity, circulation, and cellular stress. Horsetail’s proposed dual action — providing silica for structure and antioxidants for protection — is attractive because it targets two different aspects of hair health. But the clinical evidence remains weak.

For example, Ablon (2012) ran a six-month, double-blind, placebo-controlled trial in 15 women who reported thinning hair (10 on the supplement, 5 on placebo). The supplement contained shark and mollusc protein, silica from horsetail, and vitamin C. Terminal hair counts in a 4 cm² area of scalp rose in the supplement group and not in the placebo group. The study was funded by the supplement's maker. It was very small, and because the product contained several ingredients, it cannot show what horsetail contributed.

What do we really know?

If we are asking this question for ourselves, the most important point is clarity. Horsetail does contain silica and antioxidants, and these compounds have biological plausibility for supporting hair growth. Small trials of a purified silicon compound reported changes in hair brittleness and strength, and horsetail extracts scavenged free radicals in chemical laboratory tests. But no published trial has tested horsetail alone for hair. For now, horsetail is unproven for hair loss.

When we strip away marketing claims and look at the science, horsetail’s potential lies in both its silica and antioxidant content. Silica seems relevant to the structural resilience of hair fibers, while antioxidants could protect follicles from oxidative stress. But the current research does not allow us to say that horsetail extract, on its own, can reliably stimulate or restore hair growth. Both mechanisms are proposed and supported only indirectly — by a purified silicon compound and by chemical laboratory tests. Until larger, longer, horsetail-specific trials are published, horsetail remains unproven for hair.

Safety and regulatory status

Horsetail is not an approved hair treatment. In the EU it is registered only as a traditional herbal medicine to increase urine flow in minor urinary complaints, and for superficial wounds. The EU herbal monograph says it must not be used where a reduced fluid intake is recommended, for example in severe heart or kidney disease. It is not recommended during pregnancy or breastfeeding, or for children under 12. Mild stomach upset and allergic reactions (such as rash or facial swelling) have been reported (EMA HMPC, 2016). Raw horsetail also contains thiaminase, an enzyme that breaks down vitamin B1; it has caused vitamin B1 deficiency in livestock that ate the plant (Henderson et al., 1952). Talk to a doctor or pharmacist before taking horsetail, especially if you have a health condition or take other medicines.

User Experiences with Horsetail Extract for Hair Growth

Within the Tressless community, discussions around horsetail extract tend to center on whether its benefits come from silica, antioxidants, or other compounds. While laboratory studies suggest possible mechanisms—such as antioxidant activity and, for a related species, inhibition of 5α-reductase in test-tube assays—the lived experiences of users show a more cautious and mixed reality.

Several users have reported experimenting with horsetail extract, often as part of broader supplement stacks that include biotin, zinc, or saw palmetto. One recurring theme is the use of horsetail for its silica content, which is believed to strengthen hair shafts and support overall hair health. Some individuals noted that they added it to their regimen alongside bamboo extract or rosehip extract, citing the mineral’s role in collagen synthesis and tensile strength. However, these reports are usually anecdotal and often paired with multiple other interventions, making it difficult to isolate horsetail’s specific impact.

Others highlight the antioxidant properties of horsetail, sometimes combining it with green tea, beetroot powder, or vitamin C sources like acerola cherry. These users suggest that horsetail may contribute to reducing scalp inflammation and supporting circulation. A few community members observed early signs of hair thickening or decreased shedding after several weeks of supplementation, though they acknowledged the effect was subtle compared to established treatments like minoxidil and finasteride.

Not all feedback was positive. Some users were skeptical, warning that supplements like horsetail are unlikely to drive significant regrowth unless correcting a deficiency. In discussions about multi-ingredient gummies and natural blends, horsetail was frequently lumped together with biotin as something with “possible supportive benefits” but not a replacement for proven treatments. Several long-term users reported no noticeable changes in hair density, reinforcing the idea that horsetail might serve better as a complementary rather than a primary intervention.

Interestingly, there are isolated cases where users reported unexpected hair growth in non-scalp areas after combining horsetail with other botanicals such as saw palmetto and green tea. This raised questions about systemic effects and whether the changes were due to horsetail itself or to broader hormonal modulation from the supplement stack.

Taken together, the community sentiment leans toward viewing horsetail extract as a mild supportive agent rather than a transformative treatment. While some value its silica and antioxidant contributions for general hair quality, the consensus is clear that horsetail alone is insufficient for treating androgenic alopecia. Most users frame it as an “extra” layered on top of the big four—finasteride, minoxidil, ketoconazole, and microneedling—rather than a standalone solution.

References

Ablon, G. (2012). A double-blind, placebo-controlled study evaluating the efficacy of an oral supplement in women with self-perceived thinning hair. The Journal of Clinical and Aesthetic Dermatology, 5(11), 28–34. Retrieved from https://pubmed.ncbi.nlm.nih.gov/23198010/

Barel, A., Calomme, M., Timchenko, A., De Paepe, K., Demeester, N., Rogiers, V., Clarys, P., & Vanden Berghe, D. (2005). Effect of oral intake of choline-stabilized orthosilicic acid on skin, nails and hair in women with photodamaged skin. Archives of Dermatological Research, 297(4), 147–153. Retrieved from https://pubmed.ncbi.nlm.nih.gov/16205932/

Cetojević-Simin, D. D., Canadanović-Brunet, J. M., Bogdanović, G. M., Djilas, S. M., Ćetković, G. S., & Tumbas, V. T. (2010). Antioxidative and antiproliferative activities of different horsetail (Equisetum arvense L.) extracts. Journal of Medicinal Food, 13(2), 452–459. Retrieved from https://pubmed.ncbi.nlm.nih.gov/20170379/

European Medicines Agency, Committee on Herbal Medicinal Products. (2016). European Union herbal monograph on Equisetum arvense L., herba (EMA/HMPC/278091/2015). Retrieved from https://www.ema.europa.eu/en/medicines/herbal/equiseti-herba

Henderson, J. A., Evans, E. V., & McIntosh, R. A. (1952). The antithiamine action of Equisetum. Journal of the American Veterinary Medical Association, 120(903), 375–378. Retrieved from https://pubmed.ncbi.nlm.nih.gov/14927511/

Wickett, R. R., Kossmann, E., Barel, A., Demeester, N., Clarys, P., Vanden Berghe, D., & Calomme, M. (2007). Effect of oral intake of choline-stabilized orthosilicic acid on hair tensile strength and morphology in women with fine hair. Archives of Dermatological Research, 299(10), 499–505. Retrieved from https://pubmed.ncbi.nlm.nih.gov/17960402/

Tressless Community. (2020, December 27). Hair loss protocol. Retrieved from https://reddit.com/r/tressless/comments/kl1nb9/hair_loss_protocol/

Tressless Community. (2024, June 27). Obviously, all of us who are serious take antiandrogens and growth stimulants. Retrieved from https://reddit.com/r/tressless/comments/1dpu7jl/obviously_all_of_us_who_are_serious_take/

Tressless Community. (2025, March 6). Has anyone tried these? What was your experience? Retrieved from https://reddit.com/r/tressless/comments/1j4s0uc/has_anyone_tried_these_what_was_your_experience/

Tressless Community. (2024, August 6). One month green tea, saw palmetto, horsetail and zinc supplement. Retrieved from https://reddit.com/r/tressless/comments/1elkivu/one_month_green_tea_saw_palmetto_horsetail_and/

Tressless Community. (2024, August 13). Why did hair started growing on my neck after taking a mix of saw palmetto, green tea, horsetail and biotin? Retrieved from https://reddit.com/r/tressless/comments/1erk6gc/why_did_hair_started_growing_on_my_neck_after/

Tressless Community. (2020, December 19). Which of these oils would you suggest as an add-on to finasteride, nizoral, and micro-needling? Retrieved from https://reddit.com/r/tressless/comments/kfxhpy/which_of_these_oils_would_you_suggest_as_an_addon/