Medically reviewed on December 14, 2017
Scientific Name(s): Arnica montana L. In addition, other related species have been used medicinally including Arnica sororia Greene, Arnica fulgens Pursh., Arnica cordifolia Hook., Arnica chamissonis subsp. foliosa (Nutt.) Maguire. Family: Asteraceae (daisies)
Common Name(s): Arnica flos , Leopard's bane , mountain snuff , mountain tobacco , sneezewort
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.
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.
Contraindications have not been identified.
Uterine stimulant action. Avoid use.
None well documented.
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.
The plant is poisonous and ingestion can cause gastroenteritis, dyspnea, cardiac arrest, and death.
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. 1 , 2 , 3 , 4 , 5
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 include the treatment of surgical or accidental trauma, as an analgesic, and in the treatment of postoperative thrombophlebitis and pulmonary emboli. Arnica has been applied externally to 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. A. montana and A. chamissonis spp foliosa have been approved in the Complete German Commission E Monographs for external use. 6 , 7 , 8 , 9 , 10
A number of flavonoid glycosides have been identified in arnica. Flavonoids (0.4% to 0.6%) include the following: betuletol, eupafolin, flavonol glucuronides, hispidulin, isorhamnetin, luteolin, patuletin, spinacetin, tricin, 3,5,7,-trihydroxy-6,3',4'-trimethoxyflavone, kaempferol, quercetin, kaempferol and quercetin derivative, jaceosidin, and pectolin-arigenin. Isomeric alcohols include arnidiol and foradiol. 4 , 5 , 8 , 11 , 12 , 13
Terpenoids in arnica include the following: arnifolin, arnicolide, and the sesquiterpenes helenalin (and derivatives) and dihydrohelenalin. The pseudoguaianolide ester helenalin methacrylate has been isolated from the flowers. 3 , 9 , 12 , 14 , 15 The quantity of sesquiterpene lactones varies widely among species and geographical location, making standardization of preparations difficult. The European Pharmacopoeia recommends a minimum sesquiterpene lactone content of 0.4% in A. montana preparations used as herbal medicines. 9
Amines present in the plant are betaine, choline, and trimethylamine. Coumarins include scopoletin and umbelliferone. 12 Carbohydrates, such as mucilage and polysaccharides (eg, inulin), are found in arnica. Two homogeneous polysaccharides include an acidic arabino-3,6-galactan-protein and a neutral fucogalactoxyloglucan. Further polysaccharide isolation has been performed on a group of water-soluble acidic heteroglycans. 3 , 16 , 17
Volatile oils (0.3% to 1%) may be obtained from rhizomes and roots or from flower parts and are used in perfume. Constituents in the oil include thymol, its derivatives, and fatty acids (eg, palmitic, linoleic, myristic, linolenic). The fatty acid content in arnica leaf essential oil has been evaluated as well. 3 , 5 , 8 , 18 , 19 Other components found in arnica include bitter compound arnicin, caffeic acid, carotenoids (alpha- and beta-carotene, cryptoxanthin, lutein), phytosterols, resin, tannins, lignans, and anthoxanthine. 3 , 5 , 8 , 20 , 21
Uses and Pharmacology
Controversy exists concerning evaluations of the clinical efficacy of homeopathic arnica using evidence-based analyses and the existence of a placebo effect. 22 , 23 , 24 , 25 , 26 Although topical arnica preparations differ from homeopathic arnica, outcome measures such as pain, inflammation, and coagulation assays can be used as a standard measurement of effect. 22 Criticisms of clinical trials include publication bias, sample size, and intention-to-treat analysis. 23 , 27 , 28 , 29 , 30 , 31Inflammation
Animal models show both positive and negative anti-inflammatory responses to arnica. 32 , 33 , 34 A systematic review of trials prior to October 1997 found no evidence for arnica in reducing inflammation. 23 Further trials revealed no difference compared with placebo in swelling or wrist circumference following carpal tunnel surgery, 35 , 36 equivalence (no difference) to diclofenac (50 mg 3 times daily) for swelling after foot surgery, 37 and no difference in swelling after knee surgery except for cruciate ligament surgery (pooled data from 3 individual trials). 38 Overall, there is not sufficient evidence to support the use of arnica as an anti-inflammatory agent. 10 , 23 , 39 , 40Pain
A systematic review of trials prior to October 1997 found no evidence for arnica as an analgesic. 23 Studies evaluating the efficacy of arnica gel compared with ibuprofen gel in osteoarthritis suggest equivalence. 41 , 42 However, methodological weaknesses exist in the studies. 40 No difference in pain was evident for arnica in knee surgery, 38 foot surgery, 37 tonsillectomy (for days 1 to 10 postsurgery), 43 or surgery for carpal tunnel syndrome (for the first week after surgery) versus placebo. 35 , 36Bruising
The sesquiterpene lactones helenalin and 11-alpha, 13-dihydrohelenalin have been shown in vitro to inhibit platelet aggregation by interacting with platelet sulfhydryl groups. 44 However, arnica did not affect blood coagulation parameters in a randomized, controlled trial. 39 , 45 , 46
No difference was found in arnica compared with placebo for laser-induced or surgical bruising. 36 , 47 , 48 , 49 Following rhytidectomy, a decrease in bruising was observed on days 1 and 7, but not days 5 and 10. 39Muscle stiffness/marathon running
Pooled data from 2 trials evaluating muscle soreness and cell damage in marathon runners reached statistical significance for muscle soreness, but found no difference in relevant cellular enzymes. 50 A further trial reported no difference for muscle soreness in marathon runners. 40Immune system effects
Arnica contains a group of polysaccharides with 65% to 100% galacturonic acid that can inhibit the complementary system, thereby modifying the immune system response. 17 , 51 , 52 Marked enhancement of phagocytosis and stimulation of macrophages to excrete tumor necrosis factor in vivo has been demonstrated. 16 , 53 Sesquiterpene lactones have affected immune system markers, such as natural killer factor and interleukin, in mice. 32 Clinical applications for these findings have not been reported.
Arnica is classified as an unsafe herb by the US Food and Drug Administration because of its toxicity and should not be administered orally or applied to broken skin where absorption can occur. 10 , 54Topical
No consensus exists on topical dosing, and evidence from clinical trials is lacking to support therapeutic dosing. 10 , 23 , 39 Experiments show absorption of active chemical constituents to be dependent on the concentration and form of preparation. Microemulsion preparations exhibit greater absorption, as do more concentrated forms of the tincture. 9 , 55 Creams typically contain 15% arnica oil and salves have 20% to 25% of arnica oil. 10Homeopathic
Clinical evidence is lacking to support therapeutic dosing. Less concentrated strengths, such as 200 C, 1 M (1,000 C), and 10 M (10,000 C), are recommended for use in surgery. As paradoxical effects can be observed, such as causing bleeding instead of preventing bruising, preoperative homeopathic use of arnica should be limited to a few doses. 54 (The notation X is sometimes used for the strength of homeopathic arnica; the ratio of C:X is 2:1. 54 C = centesimal: potency based on the ratio of 1 part substance to 99 parts dilution. Designated with a C [or left blank in Europe] after the remedy name. C potencies are considered medium potencies. C potency is often used for seasonal problems and chronic conditions. M = millesimal: potency based on the ratio of 1 part substance to 1,000 parts dilution. Designated with a M after the remedy name. M potencies are considered high potencies. M potency is used by practitioners for constitutional treatment. 56 )
None well documented. The potential for interactions with anticoagulants has been described; however, no evidence of increased bleeding times or changes in coagulation assay tests were observed in healthy volunteers. 39 , 46
Homeopathic doses of arnica are unlikely to exert any adverse reactions due to the minimal amount ingested. 39 Oral ingestion of arnica (eg, tincture, flowers, roots, rhizomes) causes stomach pain, diarrhea, and vomiting, and irritates the mucous membranes. 4 , 9 No adverse events have been reported in clinical trials. 39 , 46 Numerous cases of allergy and contact dermatitis related to arnica have been described. Chemical and animal experimentation have proven the high-sensitizing capacity of the plant. Sesquiterpene lactones helenalin, helenalin acetate, and helenalin methacrylate are the primary sources of this type of allergy. 32 , 58 , 59 , 60 , 61
The internal use of arnica and its extracts is not recommended. 39 The plant is considered poisonous; oral use should be avoided. 3 , 4 , 10 , 12 The helenolide constituents of arnica are cardiotoxic, as determined in animal studies. 4 , 12 Homeopathic use should be implemented with caution.
Gastroenteritis has occurred with high oral dosages; dyspnea and cardiac arrest may occur and result in death. The flowers and roots of the plant have caused vomiting, drowsiness, and coma when eaten by children. 4 , 10 , 39 , 46 A tincture of 30 mL reportedly produced serious, but not fatal, effects. 5 Gastric lavage or emesis followed by supportive treatment has been recommended. 62
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