Horsetails are the only remaining genus in the plant class Equisetopsida within the ferns. In particular, the field horsetail (Equisetum arvense) has a history as a medicinal plant. A special ingredient is silicates, which give the plant stability.
At least 229 different chemical substances have been isolated from this plant, most of them flavonoids. Due to their structure, these substances have potentially antimicrobial, anti-inflammatory, antidiabetic, hepatoprotective, diuretic abilities and are potential antioxidants [1, 6].
In traditional medicine, horsetail was used for drainage, kidney disease, blader sludge and thus for the "cleansing" of blood, and also locally for wound care. Its use for "rheumatism" has also been transmitted. Standardised preparations are not available.
In the MMI Pharm Index, 11 active ingredients and groups were found for horsetail: mixed extract of marshmallow root, oak bark, chamomile flowers, dandelion herb, horsetail herb, yarrow herb and walnut leaves (4:2:3:4:5:4:4), mixed extract of goldenrod, goose cinquefoil and horsetail herb (4.2:1,4:1), horsetail leaves-, -stem juice, horsetail herb, horsetail herb extract, horsetail herb extract; extracting agents: water, horsetail herb, FE o.w.A., horsetail herb glycerol extract, horsetail herb pressed juice, horsetail herb powder, horsetail herb, TE o.w.A. (preparations of ATC Group C03XP01 – horsetail herb). Of 37 preparations, mainly external care products and dietary supplements, four are subject to pharmacy requirements: Eviprostat N, enteric-coated tablet, Evers GmbH & Co KG, Pharmazeutische Fabrik, Imupret® N Dragees, Bionorica SE, Imupret® N Tropfen, Bionorica SE, Solidagoren® Liquid, Dr. Gustav Klein GmbH & Co. KG medicinal plant preparations.
The PubMed search on 04.05.2025 remained very poor with "Horsetail herb" (6 hits, 1 with "Rheumatism*"), "Horsetail" without hits and "Equisetum" with 555 hits (without further restrictions, 2 of them with "Rheumatism*" and 7 with "Arthritis"). Only in the last 10 years has scientific interest in the plant increased and in recent years some reports related to the question have appeared. Most of the literature references refer to the proof of composition.
KYNA (kynurenic acid) is named as a potentially effective substance, which can also be detected in other plants such as peppermint [7]. Since KYNA levels are low in patients with untreated rheumatoid arthritis [4], it is hoped that substitution will improve the symptoms. An actual controlled use in a study has not been published.
A study in six rats with adjuvant-induced arthritis showed a dose-dependent improvement in clinical findings, histology and cytokine levels by Equisetum diffusum whole plant methanol extract (EDME). The authors hypothesized that this extract could also have positive effects on human rheumatoid arthritis [5]. In the antigen-induced mouse arthritis model, an aqueous extract of Equisetum giganteum was able to improve numerous surrogate parameters [2]. In vitro, Equisetum arvense extract was shown to have an inhibitory effect on lymphocyte proliferation and activation as well as cytokine production [3].
The group of horsetail plants is a substance traditionally used for many indications, including "rheumatism". Standardised preparations are not available. There are no studies on their use in humans. The extracted ingredients could theoretically have an influence on rheumatic diseases as flavonoids, antioxidants or a substitute source for KYNA. However, a transfer of the available data from arthritis animal models to rheumatoid arthritis is not justified.
In horses, the consumption of horsetail can lead to the so-called dizziness disease. Toxic effects have also been reported in humans.
Based on the data, the use of horsetail cannot be recommended for inflammatory, rheumatic or degenerative diseases. However, the data motivate further scientific consideration of the plant group.
1. Dormousoglou M, Efthimiou I, Antonopoulou M et al. (2022) Investigation of the Genotoxic, Antigenotoxic and Antioxidant Profile of Different Extracts from Equisetum arvense L. Antioxidants (Basel) 11
2. Farinon M, Lora PS, Francescato LN et al. (2013) Effect of Aqueous Extract of Giant Horsetail (Equisetum giganteum L.) in Antigen-Induced Arthritis. Open Rheumatol J 7:129-133
3. Grundemann C, Lengen K, Sauer B et al. (2014) Equisetum arvense (common horsetail) modulates the function of inflammatory immunocompetent cells. BMC Complement Altern Med 14:283
4. Moulin D, Millard M, Taieb M, et al. (2024) Counteracting tryptophan metabolism alterations as a new therapeutic strategy for rheumatoid arthritis. Ann Rheum Dis 83:312-323
5. Sarkar S, Modak D, Roy SK et al. (2025) Equisetum diffusum whole plant methanol extract attenuates rheumatoid arthritis by modulating the expression of key inflammatory biomarkers in rat models. Sci Rep 15:9950
6. Sureshkumar J, Jenipher C, Sriramavaratharajan V et al. (2023) Genus Equisetum L: Taxonomy, toxicology, phytochemistry and pharmacology. J Ethnopharmacol 314:116630
7. Zgrajka W, Turska M, Rajtar G et al. (2013) Kynurenic acid content in anti-rheumatic herbs. Ann Agric Environ Med 20:800-802
Stand: 11.03.2026