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VITAMINS & SUPPLEMENTS · GUIDE

Silica (Silicon): Hair, Skin, Nails and Bone Claims Checked

What small trials found for silica (silicon) and orthosilicic acid in hair, skin, nails and bone, what horsetail is traditionally used for, and why no upper limit does not mean safe.

Content last updated . This page has not been medically reviewed.

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Quick answer
Silica or silicon supplements, including "orthosilicic acid" and horsetail products, are marketed for hair, skin, nails and bones. In the sources we read, the human evidence is a few small trials of one form, a population study that cannot prove cause, and animal work. We found no large trial showing better hair, nails or fewer fractures. This page gives information only.

How the terms are used

Silicon is the element, and trial reports use "mg Si" for the amount of silicon. Orthosilicic acid is a form of silicon; trial authors describe choline-stabilized orthosilicic acid ("ch-OSA") as a bioavailable form. [1] Evidence for one form does not carry over to other silica products such as plant extracts, and we did not find trials of those in the sources read.

Evidence labels: preliminary means small trials; observational means people were observed, not assigned; preclinical means animal or lab work; Proper evidence not found means we searched and found nothing usable.

What the research found

6 findings · 6 limited or unclearThe colour follows the evidence label on each card.

  1. Skin, nails, hair

    Preliminary

    50 women with sun-damaged facial skin took 10 mg Si a day as ch-OSA or placebo for 20 weeks. Skin roughness changed more in the ch-OSA group. Self-rated nail and hair brittleness scores fell compared with each woman's own baseline, not directly against placebo. [1]

  2. Hair

    Preliminary

    48 women with fine hair took 10 mg Si a day as ch-OSA or placebo for 9 months. Hair tensile strength measures were better preserved and cross-sectional area increased. These are lab measures of hair, not how hair looks or how much sheds. [2]

  3. Bone, trial

    Preliminary; biomarkers

    136 women with low spine bone density all took calcium and vitamin D3, plus ch-OSA at 3, 6 or 12 mg Si or placebo for 12 months. Only one bone-formation marker (PINP) was significantly higher, at 6 and 12 mg, and lumbar spine bone density did not change significantly. [3]

  4. Bone, diet

    Observational

    In 2,847 Framingham adults, higher dietary silicon went with higher hip bone density in men and premenopausal women, not in postmenopausal women. This was a one-time snapshot and cannot show cause. [4]

  5. Bone, animals

    Preclinical

    A 2024 umbrella review of animal studies said it was hard to define an effective amount, and that the level that consistently helped is likely unfeasible to reach in humans. [5]

  6. Other silica forms

    Insufficient

    Proper evidence not found for products other than ch-OSA in the PubMed searches we ran (orthosilicic acid and hair or nails; silicon and bone density).

The two hair and skin trials share several authors, [1] [2] and our searches found no independent repeat. Treat the findings as early.

Horsetail

Horsetail is a plant often sold as a silica source. The European Medicines Agency summary describes horsetail herb as used traditionally for minor urinary problems and superficial wounds, only in adults and adolescents over 12, and says clinical trial evidence is insufficient. [6] It does not describe use for hair or nails. EMA lists allergic reactions and mild stomach complaints as side effects. [6]

Hair, skin and nail changes

Brittle nails and hair shedding can have medical causes. See Skin and hair research and evidence, Hair shedding and thinning and Nutrition for skin and hair. Biotin and collagen claims are on Collagen, biotin and beauty supplements. For minerals in this area see Minerals for hair, skin and nails, and for bone see Osteoporosis and bone health.

Frequently asked questions

Does silica make hair and nails stronger?

Two small trials of one form, ch-OSA, reported better hair strength measures and lower self-rated brittleness. [2] [1] We found no independent repeat or large trial.

Does silica help bones?

A 12-month trial added ch-OSA to calcium and vitamin D and saw a rise in one bone-formation marker, but no significant change in lumbar spine bone density. [3]

Is horsetail a good silica supplement?

EMA's summary does not describe horsetail for hair or nails; it describes traditional use for minor urinary problems and wounds. [6]

Is there an upper limit for silicon?

Health Canada's page lists none because suitable data were lacking. [7] That does not make high amounts safe.

Who should ask a clinician first?

Anyone who is pregnant, breastfeeding, giving it to a child, taking medicines, living with kidney or liver disease, or having surgery. The sources we read did not cover these situations.

More details: evidence, limits and cautions

The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.

Upper limits and safety
Health Canada's reference-values page lists silicon but gives no upper limit, noting that limits could not be established because of a lack of suitable data. [7] That is not proof of safety; it means the data are missing. The sources we read did not cover supplements in pregnancy, children, kidney or liver disease, or interactions with medicines, so ask a clinician or pharmacist. See Medication interactions and Supplements before surgery. The FDA says it is not authorized to approve dietary supplements for safety and effectiveness before they are marketed. [8] See Quality testing and certifications.
References
  1. Barel A et al., Effect of oral intake of choline-stabilized orthosilicic acid on skin, nails and hair in women with photodamaged skin, Arch Dermatol Res 2005 (abstract read). Read 2026-10-23.
  2. Wickett RR et al., Effect of oral intake of choline-stabilized orthosilicic acid on hair tensile strength and morphology in women with fine hair, Arch Dermatol Res 2007 (abstract read). Read 2026-10-23.
  3. Spector TD et al., Choline-stabilized orthosilicic acid supplementation as an adjunct to calcium/vitamin D3 stimulates markers of bone formation in osteopenic females, BMC Musculoskelet Disord 2008 (abstract read). Read 2026-10-23.
  4. Jugdaohsingh R et al., Dietary silicon intake is positively associated with bone mineral density in men and premenopausal women of the Framingham Offspring cohort, J Bone Miner Res 2004 (abstract read). Read 2026-10-23.
  5. Pritchard A, Nielsen BD, Silicon supplementation for bone health: an umbrella review attempting to translate from animals to humans, Nutrients 2024 (abstract read). Read 2026-10-23.
  6. European Medicines Agency, Equiseti herba (horsetail) herbal medicine summary (summary updated 28 April 2016; read through a web-fetch tool that summarizes pages). Read 2026-10-23.
  7. Health Canada, Dietary reference intakes tables: reference values for elements (page dated 2025-11-19; read through a web-fetch tool that summarizes pages). Read 2026-10-23.
  8. US FDA, Information for Consumers on Using Dietary Supplements. Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.