Field horsetail contains thiaminase, an enzyme that degrades thiamine (vitamin B1); prolonged or excessive use can cause thiamine deficiency — symptoms include neurological problems and weight loss. This risk is greatest with repeated large doses or prolonged use. The plant also contains nicotine at low levels and silica compounds. Not recommended for children or during pregnancy and breastfeeding. People with impaired kidney function should avoid use, as diuretic effects may worsen fluid and electrolyte imbalance. Caution with concurrent diuretic medications. The EMA herbal monograph recognises traditional use at appropriate short-term doses in adults only (European Medicines Agency, 2016; Sandhu et al., 2010).

Safety note^{[11, 12, 13, 14, 15]}Caution

Duke (2002) rates horsetail as + (moderate caution) and notes clinical evidence (score 2) for its diuretic and wound-healing (vulnerary) activities, consistent with Commission E approval. High silica content may strengthen connective tissue, hair, and nails. Dose: 6 g dried herb daily as tea or in capsules. Horsetail contains thiaminase (breaks down vitamin B1) and an unidentified neurotoxin — it should not be taken long-term or in large quantities. Not for use in patients with edema due to cardiac or renal insufficiency, and avoid in children under 12 (Duke, 2002).

References

REF-1398, REF-0727, REF-1399, REF-1400, REF-1401, REF-1402, REF-1403, REF-1404, REF-1405, REF-1406

References & Sources

Hegedus, C., Muresan, M., Badale, A., Bombicz, M. and others (2020) 'SIRT1 Activation by Equisetum arvense L. (Horsetail) Modulates Insulin Sensitivity in Streptozotocin Induced Diabetic Rats', Molecules, 25(11), pp. 2541. doi:10.3390/molecules25112541 Preclinical
https://doi.org/10.3390/molecules25112541
Dragos, D., Gilca, M., Gaman, L., Vlad, A., Iosif, L. et al (2017) 'Phytomedicine in Joint Disorders', Nutrients, 9(1), pp. 70. doi:10.3390/nu9010070 Traditional / reference
https://doi.org/10.3390/nu9010070
Grundemann, C., Lengen, K., Sauer, B., Garcia-Kaufer, M. and others (2014) 'Equisetum arvense (common horsetail) modulates the function of inflammatory immunocompetent cells', BMC Complementary and Alternative Medicine, 14, pp. 283. doi:10.1186/1472-6882-14-283 Preclinical
https://doi.org/10.1186/1472-6882-14-283
Wang, L., Zhang, L., Zheng, G. and Luo, H (2021) 'Equisetum arvense L aqueous extract: a novel chemotherapeutic supplement for treatment of human colon carcinoma', Archives of Medical Science, 19(5), pp. 1472-1478. doi:10.5114/aoms/138146 Preclinical
https://doi.org/10.5114/aoms/138146
Jeong, S.Y., Yu, H.S., Ra, M.J., Jung, S.M. and others (2023) 'Phytochemical Investigation of Equisetum arvense and Evaluation of Their Anti-Inflammatory Potential in TNFalpha/INFgamma-Stimulated Keratinocytes', Pharmaceuticals, 16(10), pp. 1478. doi:10.3390/ph16101478 Preclinical
https://doi.org/10.3390/ph16101478
Klncalp, S., Ekiz, F., Basar, O., Coban, S. and others (2012) 'Equisetum arvense (Field Horsetail)-induced liver injury', European Journal of Gastroenterology & Hepatology, 24(2), pp. 213-214. doi:10.1097/MEG.0b013e32834e7ff0 Preclinical
https://doi.org/10.1097/MEG.0b013e32834e7ff0
Maeda, H., Miyamoto, K. and Sano, T (1997) 'Occurrence of dermatitis in rats fed a cholesterol diet containing field horsetail (Equisetum arvense L.)', Journal of Nutritional Science and Vitaminology, 43(5), pp. 553-563. doi:10.3177/jnsv.43.553 Preclinical
https://doi.org/10.3177/jnsv.43.553
Saslis-Lagoudakis, C.H., Bruun-Lund, S., Iwanycki, N.E., Seberg, O. and others (2015) 'Identification of common horsetail (Equisetum arvense L.; Equisetaceae) using Thin Layer Chromatography versus DNA barcoding', Scientific Reports, 5, pp. 11942. doi:10.1038/srep11942 Preclinical
https://doi.org/10.1038/srep11942
Mimica-Dukic, N., Simin, N., Cvejic, J., Jovin, E. and others (2008) 'Phenolic compounds in field horsetail (Equisetum arvense L.) as natural antioxidants', Molecules, 13(7), pp. 1455-1464. doi:10.3390/molecules13071455 Preclinical
https://doi.org/10.3390/molecules13071455
Tufarelli, V., Baghban-Kanani, P., Azimi-Youvalari, S., Hosseintabar-Ghasemabad, B. and others (2021) 'Effects of Horsetail (Equisetum arvense) and Spirulina (Spirulina platensis) Dietary Supplementation on Laying Hens Productivity and Oxidative Status', Animals, 11(2), pp. 335. doi:10.3390/ani11020335 Preclinical
https://doi.org/10.3390/ani11020335
Carneiro, D.M., Marques, L.C., Velasques, L.O. et al (2016) 'Randomized, double-blind clinical trial to assess the acute diuretic effect of Equisetum arvense (Field Horsetail) in healthy volunteers'. doi:10.1155/2014/760683 Randomized trial
https://doi.org/10.1155/2014/760683
European Medicines Agency (2016) 'European Union herbal monograph on Equisetum arvense L., herba'. Available at: https://www.ema.europa.eu/en/documents/herbal-monograph/final-european-union-herbal-monograph-equisetum-arvense-l-herba_en.pdf Traditional / reference
https://www.ema.europa.eu/en/documents/herbal-monograph/final-european-union-herbal-monograph-equisetum-arvense-l-herba_en.pdf
http://LatvijasDaba.lv (n.d.) 'tīruma kosa – Equisetum arvense L'. Available at: http://LatvijasDaba.lv Traditional / reference
http://LatvijasDaba.lv
Royal Botanic Gardens, Kew (n.d.) 'Equisetum arvense L'. Available at: https://powo.science.kew.org/taxon/urn:lsid:http://ipni.org:names:17003330-1 Traditional / reference
https://powo.science.kew.org/taxon/urn:lsid:http://ipni.org:names:17003330-1
Sandhu, N.S., Kaur, S. and Chopra, D (2010) 'Equisetum arvense: pharmacology and phytochemistry — a review', 3(3), pp. 146--150. Traditional / reference
Find this source

Generated June 22, 2026 from omniasana.bio