The perennial arnica grows from 0.3 to 0.6 m. Oval-shaped, opposite leaves form a basal rosette close to the soil surface. Arnica has bright yellow, daisy-like flowers that, when dried, are the primary parts used. However, the roots and rhizomes are also utilized. Arnica is native to the mountainous regions of Europe and southern Russia. The unrelated plant monkshood (Aconitum spp.) is referred to as wolf's bane.
What is it used for?
Arnica and its extracts have been widely used in folk and homeopathic medicine as a treatment for acne, boils, bruises, rashes, sprains, pains, and other wounds. Overall, there does not appear to be sufficient evidence to support the use of arnica as an anti-inflammatory or analgesic agent, or to prevent bruising; however, heterogeneity of doses and delivery forms (as well as indications) in available clinical studies makes generalizations difficult.
Internal and external preparations made from the flowering heads of arnica have been used medicinally for hundreds of years. Arnica was used extensively in European folk medicine and alcoholic tinctures were produced by early North American settlers to treat sore throats, as a febrifuge, and to improve circulation. Homeopathic uses included the treatment of surgical or accidental trauma, as an analgesic, and in the treatment of postoperative thrombophlebitis and pulmonary emboli. It has been used externally for acne, bruises, sprains and muscle aches. In addition, it has been used as a general topical counterirritant and a CNS stimulant, as well as an antibacterial for abrasions and gunshot wounds. Arnica is also an ingredient in hair tonics, dandruff treatments, perfumes, and cosmetics.
What is the recommended dosage?
Arnica should not be administered orally or applied to broken skin where absorption can occur. No consensus exists on topical dosing, and evidence from clinical trials is lacking to support therapeutic dosing. In homeopathic use, less concentrated strengths such as 200 C, 1 M (1,000 C), and 10 M (10,000 C) (C = centisimal dilution [1 part in 100]; M = millesimal dilution [1 part in 1,000]), are recommended for use pre- and postsurgically; clinical evidence is lacking to support therapeutic dosing.
Homeopathic doses of arnica are unlikely to exert any adverse reactions because of the minimal amount ingested. Arnica irritates mucous membranes and causes stomach pain, diarrhea, and vomiting. Allergy and contact dermatitis have been reported.