One of the most widely known folk remedies, arnica (Arnica montana) is a perennial herb known for its medical properties. Northern European people used it for centuries to treat all types of injuries related to falls, bruises, aches, and sprains. It was especially famous among ancient cultures as a popular remedy for horse falls, although more traditional uses include the treatment of fever and sore throat. Arnica can also be chewed, and it’s thus called “mountain tobacco” in France (Tabac des Vosges). It is a small, pleasantly-scented flowering plant whose flowers are usually brightly yellow or orange colored. Most of its essential oils and chemical constituents are contained within those flowers, that emit a faint tobacco smell when wet. Arnica pertains to the sunflower family (asteracee). It grows on alpine meadows and upland regions at high altitudes (up to 10,000 feet). Although is a rare herb, it can grow even in nutrient poor soils if they’re acidic enough. Armed with the right hiking equipment, trekking enthusiasts often collect it during their trips since it grows spontaneously in Northern Europe, France, Spain, Germany, and Russia.
Medical Uses and Chemical Constituents
The active chemicals in arnica are sesquiterpene lactones (0.2-0.8 percent), arnicine, gallic acid, tannins, essential oils, flavanone glycosides, thymol and the toxin helenalin. This last constituent has hepatotoxic effects and may act as a local irritant when applied on the skin. For this reason, this herb should never be ingested since it may cause gastroenteritis and gastrointestinal bleedings. Topical application should not be prolonged due to a risk of local inflammations and allergic reactions. Arnica should never be applied on open wounds and is not recommended during pregnancy.
Arnica’s principal indication is the treatment of bruises and ecchymoses, and it’s usually applied as a cream, ointment, gel or other topical medication. It’s also widely used to treat sore muscles and strains, and it’s so effective that it’s often employed for racehorses after strenuous training sessions and workouts. Although most studies proved arnica to be effective, data is often sparse and contradictory. Several studies did, in fact, examined the effects of the homeopathic doses which were obviously ineffective, highlighting a general propensity for structural bias in the scientific analysis of herbal remedies. It is pointless to put the effectiveness of a full dose of the herb and a homeopathic medicine for tooth pain on the same level. More recent studies identified reliable evidence about arnica’s effectiveness in treating osteoarthritis and help speed recovery time after knee surgery. So far no mechanism that fully explains how exactly this herb works has ever been found. Among the various hypotheses, it has been suggested that due to their nonpolar structure, sesquiterpene lactones may penetrate skin layers and reach the site of inflammation. Once there, these active compounds may reduce the pain by penetrating the cell membranes of white blood cells that are attracted by inflammatory processes, actually preventing them from releasing additional proinflammatory cytokines.
The essential oils found in this plant can be used as preservatives due to the antimicrobic and fungicide activity of thymol. The toxin helenalin is currently being investigated as a potential antitumor agent because some studies showed its in vitro activity as immunomodulant. It also has anti-inflammatory and cytotoxic properties. Arnica tincture can also be used as a counterirritant to treat soreness. Patients should always seek their pharmacist or doctor’s advice before taking arnica.
Article by Dr. Claudio Butticè, Pharm.D.
- Auerbach. “Wilderness Medicine”, 6th ed. Philadelphia, PA: Mosby; 2011.
- Blumenthal M, et al. “Herbal Medicine: Expanded Commission E Monographs.” Newton, Mass: Integrative Medicine Communications; 2000.
- Lyss G, et al. “The anti-inflammatory sesquiterpene lactone helenalin inhibits the transcription factor NF-kappaB by directly targeting p65″. J Biol Chem 273 (50): 33508–16. doi:10.1074/jbc.273.50.33508
- Knuesel O, Weber M, Suter A. “Arnica montana gel in osteoarthritis of the knee: an open, multicenter clinical trial.” Adv Ther. 2002 Sep-Oct;19(5):209-18.
- Karow JH, et al. “Efficacy of Arnica montana D4 for healing of wounds after Hallux valgus surgery compared to diclofenac.” J Altern Complement Med. 2008 Jan-Feb;14(1):17-25. doi:10.1089/acm.2007.0560.
- Powis G, et al. “Increased intracellular Ca2+ signaling caused by the antitumor agent helenalin and its analogues“. Cancer Chemother. Pharmacol. 34 (4): 344–350. doi:10.1007/BF00686043.
- Rudzki E, Grzywa Z. “Dermatitis from Arnica montana“. Contact Dermatitis 3 (5): 281–2. doi:10.1111/j.1600-0536.1977.tb03682.x
- Merfort I. [Arnica: new insights on the molecular mode of action of a traditional medicinal plant]. Forsch Komplementarmed Klass Naturheilkd. 2003 Apr;10 Suppl 1:45-8.
- The European Agency for the Evaluation of Medicinal Products – Veterinary Medicines Evaluation Unit “Committee for Veterinary Medicinal Products, Arnica Montana Summary Report.” EMEA/MRL/647/99 – Final, Dec 1999
- Weremczuk-Jezyna, et al. “Thymol derivatives from hairy roots of Arnica montana“. Plant Cell Reports 25 (9): 993–6. doi:10.1007/s00299-006-0157-y