Botanical supplement, aerial parts of Equisetum arvense (field horsetail), source of silica and flavonoids; in the EU registered as a traditional-use herbal medicinal product (EMA HMPC) for mild diuretic effect; sold on iHerb as silica for «skin, hair and nails»
ATC code: A11JA-HORSETAIL (Horsetail (Equisetum arvense, silica))
Brand names – supplements
NOW Horsetail, Nature's Way Horsetail, Eidon Silica, Flora Vegetal Silica
Supplements are not tested in clinical trials and are not registered as medications.
Field horsetail is a herbaceous spore plant; its aerial parts contain 5-7% water-soluble silicates and silicic-acid salts, flavonoids (isoquercitrin, kaempferol), phenolic acids and trace nicotine. HMPC in 2016 registered horsetail as a traditional-use herbal medicinal product to increase urine volume as adjunctive therapy for mild urinary complaints – strictly on the basis of traditional use, without RCTs. in 2009 rejected all silicon health claims: «healthy connective tissue», «bones», «hair and nails» applications were not supported by quality evidence. In parallel, horsetail contains thiaminase, an enzyme that destroys vitamin B1 (thiamine); long-term oral use of unprocessed horsetail caused thiamine deficiency in animal models and is documented in rare clinical case reports in humans. Modern European products steam-process the raw material to inactivate thiaminase, but quality control on the iHerb market is opaque.
The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.
Not recommended
Horsetail (Equisetum arvense) is an herb with a mild diuretic effect, sold as a remedy for "detox" and "cleansing" the body. Its benefit for this specific use has not been shown – there is no convincing evidence for horsetail-based "detoxification". The body clears waste on its own through the liver and kidneys, and you support them with enough water, sleep, and a balanced diet.
Not recommended
Field horsetail is an over-the-counter silica supplement. On iHerb it is sold as «silica for skin, hair and nails», promising collagen reinforcement, hair growth and strong nails. in 2009 rejected all silicon health claims – applications for «healthy connective tissue», «bones», «hair and nails» were not supported by quality evidence. Silicon bioavailability from horsetail is lower than from orthosilicic acid, and whether it reaches collagen fibres of skin and nails in meaningful amounts is unknown. RCTs with hard endpoints (objective hair-thickness, nail-growth rate, skin elasticity) do not exist. The 2016 HMPC monograph recognises horsetail only as a traditional-use diuretic, not as a hair or nail product. AESAN classifies horsetail as a complemento alimenticio without therapeutic indication. If horsetail was bought for «hair and nails» in the setting of hair loss, discuss with a doctor – real causes (iron deficiency, hypothyroidism, telogen effluvium, androgenetic alopecia) need blood tests and targeted treatment with minoxidil, finasteride, iron or levothyroxine, not a plant supplement.
Opens the checker prefilled with this drug. Pick the second one from your regimen.
Direct links to regulator labels. Open in a new tab.
Horsetail safety in human pregnancy has not been studied in RCTs. EMA HMPC 2016 advises against horsetail use in pregnancy because of thiaminase activity and the risk of thiamine deficiency in mother and fetus. AEMPS and AESAN advise against supplements without therapeutic indication during pregnancy.
Horsetail safety in lactation has not been studied in RCTs. EMA HMPC 2016 advises against use in lactation. Thiaminase activity can lower thiamine in breast milk.
Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.
Horsetail is evaluated for the following indications with varying evidence strength: Skin, hair and nails (supplement marketing) (evidence tier D), Body detoxification and cleansing (evidence tier D). See the full indication matrix with dosing and citations above on this page.
Common side effects of Horsetail (≥ 1 in 100): Gastrointestinal discomfort, nausea, Increased urinary frequency, Skin reactions in predisposed users. See the Safety section for uncommon and serious reactions.
FDA category N. Horsetail safety in human pregnancy has not been studied in RCTs. EMA HMPC 2016 advises against horsetail use in pregnancy because of thiaminase activity and the risk of thiamine deficiency in mother and fetus. AEMPS and AESAN advise against supplements without therapeutic indication during pregnancy.
Horsetail safety in lactation has not been studied in RCTs. EMA HMPC 2016 advises against use in lactation. Thiaminase activity can lower thiamine in breast milk.
Horsetail is contraindicated in: Pregnancy and lactation (EMA HMPC 2016); Children under 12 years; Chronic heart or renal failure with oedema requiring registered diuretics; Alcohol use disorder and malabsorption – higher thiamine-deficiency risk; Concurrent diuretics, cardiac glycosides or lithium – risk of hypokalaemia and electrolyte imbalance. Full list in the Safety section.