Health Care Professional Information

Scientific Name
Arnica montana
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Common Name

Mountain tobacco, leopard’s bane, wolf’s bane, mountain arnica

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Clinical Summary

Derived from the flowers and rhizome. The raw herb and the homeopathic arnica have been used in the treatment of bruises (1) (2) (3). In vitro studies showed that Arnica montana has antimicrobial activities (4). Conclusions from a systematic review point to insufficient evidence to support use of arnica (5). But clinical trials conducted since then suggest benefits of arnica for osteoarthritis (6) (7) (8) and reduction in postoperative swelling (9) and pain (10). However, one small study reported that arnica increased pain 24 hours after calf exercises (11). Another study found that topical arnica ointment significantly reduced bruising compared to placebo or low concentration vitamin K ointments (3).
Side effects following oral administration of the herb (but not the homeopathic preparation) include gastrointestinal distress, hypotension, tachycardia, shortness of breath, coma, and death (12) (13). Topical administration is benign, but can cause contact dermatitis, irritation, and burning (14).

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Purported Uses
  • Inflammation
  • Sprains
  • Bruise
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Constituents
  • Amines: Betaine, choline, trimethylamine
  • Carbohydrates: Mucilage, polysaccharides including inulin
  • Coumarins: Scopoletin, umbelliferone
  • Flavonoids: Betuletol, eupafolin, flavonol, glucuronides, kaempferol, luteolin, quercetin, spinacetin, tricin
  • Terpenoids: Sesquiterpenes, arnifolin, helenalin
  • Volatile Oils: Thymol
  • Other constituents: Arnicin, caffeic acid, carotenoids, phytosterols, resin, tannin
    (14)
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Mechanism of Action

Experimental studies on the effects of arnica preparations have demonstrated antimicrobial, anti-inflammatory, respiratory-stimulant, positive inotropic, and tonus increasing actions. The anti-inflammatory effects are attributed to helenalin, whose actions include a marked antiedemic effect that has been confirmed in experimental models. The external use of arnica preparations can cause dermatitis in individuals sensitized by sesquiterpenes of the helenalin type (12). One in vitro study demonstrated that a tincture prepared from A. Montana flowers and aqueous ethanol suppressed collagenase-1 (MMP1) and interstitial collagenase-13 (MMP13) mRNA levels in human articular chondrocytes. One in vitro study demonstrated that a tincture prepared from A. Montana flowers and aqueous ethanol suppressed collagenase-1 (MMP1) and interstitial collagenase-13 (MMP13) mRNA levels in human articular chondrocytes. (15) This action was attributed to the inhibition of the binding of transcription factors AP-1 and NF-kb to DNA. The enzymes MMP13 and MMP1 are thought to play a significant role in the cartilage and joint destruction and inflammation seen in osteoarthritis and rheumatoid arthritis (15). This action was attributed to the inhibition of the binding of transcription factors AP-1 and NF-kb to DNA. The enzymes MMP13 and MMP1 are thought to play a significant role in the cartilage and joint destruction and inflammation seen in osteoarthritis and rheumatoid arthritis.

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Warnings

Internal use of arnica is not advised. The effects of arnica on the lungs, heart, and uterus have not been sufficiently tested to justify the risks associated with oral use. A fatal case of poisoning has been reported following ingestion of 70 g of arnica tincture. The FDA considers oral Arnica an unsafe herb. External use appears to pose no risk.
(13) (16)

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Adverse Reactions

Common (oral): GI distress, tachycardia, shortness of breath, coma and death
Infrequent (topical): Contact dermatitis, irritation, burning
(5)

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Herb-Drug Interactions

Antihypertensives: Arnica may reduce hypotensive effects.
Anticoagulants / Antiplatelet agents: Arnica may potentiate the anticoagulant effect due to the coumarin constituents. This effect has not been documented in humans. Use with caution.

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Literature Summary and Critique

Adkison JD, et al. The effect of topical arnica on muscle pain. Ann Pharmacother. 2010 Oct;44(10):1579-84.
This was a randomized, double-blind, placebo-controlled trial that enrolled 53 subjects. The goal of this study was to to determine whether topical Arnica montana cream could decrease subjective leg pain following calf raises. Each patient received two tubes of cream: one containing arnica and the other containing placebo. The creams were applied to the right or left calf (as directed by labels on the tubes) immediately after exercise, and again 24 and 48 hours post-exercise. Subjects used an analog scale to rate pain severity at baseline, and at 24, 48, and 72 hours after exercising. At 48 hours post-exercise, ankle range of motion and muscle tenderness were also measured. There were no significant differences in pain scores for the legs treated with the arnica or placebo creams at baseline. However, 24 hours post-exercise, pain scores for the arnica-treated legs were significantly higher than placebo (p<0.005). Pain scores for the arnica and placebo creams were not significantly different at 48 and 72 hours post-exercise. No significant differences in ankle range of motion or muscle tenderness were detected for the two treatments.

Leu S, et al. Accelerated resolution of laser-induced bruising with topical 20% arnica: a rater-blinded randomized controlled trial. Br J Dermatol. 2010 Sep;163(3):557-63.
This double-blind, randomized, controlled study investigated the effect of a topical arnica formula on the resolution of skin bruising. The study enrolled 16 patients who then had two bruises created on each bilateral upper inner arm, by a pulsed dye laser. One of 4 topical agents (5% vitamin K, 1% vitamin K/0.3% retinol, arnica, or white petrolatum) was randomly assigned to treat one of the 4 bruises. Each treatment was applied to the assigned bruise twice daily under occlusion, for 2 weeks. A dermatologist rated the severity of the bruises at baseline and after 2 weeks of treatment. Improvement in bruise severity score was found to be significantly greater for arnica than for white petrolatum (p=0.003) or 1% vitamin K/0.3 retinol (p=0.01). Bruise reduction was also found to be nominally better with arnica than with 5% vitamin K, but the difference was not statistically significant. The investigators concluded that topical arnica ointment may reduce bruising more effectively than placebo or low concentraiton vitamin K formulations.

Ross SM. Osteoarthritis: a proprietary Arnica gel is found to be as effective as ibuprofen gel in osteoarthritis of the hands. Holist Nurs Pract. 2008 Jul-Aug;22(4):237-9.
This study was a randomized, double-blind, controlled, multicenter study that enrolled 204 outpatients with osteoarthritis of the interpharyngeal joints. Patients were randomized to receive 5% topical ibuprofen or arnica gel 3 times daily for 3 weeks. Patients were also allocated a preset number of acetaminophen tablets to be used as a “rescue treatment” if the pain was unbearable. Study results indicated that the arnica gel was comparable to ibuprofen gel with respect to hand functional capacity, pain intensity, number of painful joints, duration and severity of morning stiffness, and acetaminophen consumption. The researchers concluded that arnica gel can be used as an alternative to ibuprofen gel in patients with osteoarthritis of the hand.

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Dosage (Inside MSKCC Only)
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References
  1. Blumenthal, et al. Herbal Medicine, Expanded Commission E Monographs. Austin: American Botanical Council; 2000.
  2. Wichtl M. Herbal Drugs and Phytopharmaceuticals. Boca Raton: CRC Press; 1994.
  3. Leu S, Havey J, White LE, Martin N, Yoo SS, Rademaker AW, Alam M. Accelerated resolution of laser-induced bruising with topical 20% arnica: a rater-blinded randomized controlled trial. Br J Dermatol. 2010 Sep;163(3):55763.
  4. Koo H, et al. In vitro antimicrobial activity of propolis and Arnica montana against oral pathogens. Arch Oral Biol. 2000 Feb;45(2):141-8.
  5. Ernst E, Pittler MH. Efficacy of homeopathic arnica: a systematic review of placebo-controlled clinical trials. Arch Surg. 1998 Nov;133(11):1187-90.
  6. Knuesel O, et al. Arnica montana gel in osteoarthritis of the knee: an open, multicenter clinical trial. Adv Ther. 2002 Sep-Oct;19(5):209-18.
  7. Widrig R, Suter A, Saller R, Melzer J. Choosing between NSAID and arnica for topical treatment of hand osteoarthritis in a randomized, double-blind study. Rheumatol Int 2007;27(6):585-91.
  8. Ross SM. Osteoarthritis: a proprietary Arnica gel is found to be as effective as ibuprofen gel in osteoarthritis of the hands. Holist Nurs Pract. 2008 JulAug;22(4):237-9.
  9. Brinkhaus B, Wilkens JM, Ludtke R, et al. Homeopathic arnica therapy in patients receiving knee surgery: results of three randomized double-blind trials. Complement Ther Med 2006;14(4):237-46.
  10. Robertson A, Suryanarayanan R, Banerjee A. Homeopathic Arnica montana for post-tonsillectomy analgesia: a randomized placebo control trial. Homeopathy 2007 96(1):17-21.
  11. Adkison JD, Bauer DW, Chang T. The effect of topical arnica on musclepain. Ann Pharmacother. 2010 Oct;44(10):1579-84.
  12. Schulz V, et al. Rational Phytotherapy, A Physician's Guide to Herbal Medicine, 3rd ed. New York: Springer; 1996.
  13. US FDA / CFSAN / Office of plant and dairy foods and beverages. Poisonous Plant Database - Vascular Plant List [online] 1999 May 14 [cited 2001 July 12]. Available from: URL: http://vm.cfsan.fda.gov/~djw/plantnam.html
  14. Newall CA, et al. Herbal Medicines: A Guide for Health-Care Professionals. London: Pharmaceutical Press; 1996.
  15. Jäger C, Hrenn A, Zwingmann J, Suter A, Merfort I. Phytomedicines prepared from Arnica flowers inhibit the transcription factors AP-1 and NF-kappaB and modulate the activity of MMP1 and MMP13 in human and bovine chondrocytes. Planta Med. 2009 Oct;75(12):1319-25. Epub 2009 May 8.
  16. Brinker F. Herb Contraindications and Drug Interactions, 3rd ed. Sandy (OR): Eclectic Medical Publications; 2001.
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Consumer Information

How It Works

Bottom Line: There is some evidence that arnica is effective in bruise healing and osteoarthritis. It has not been studied for anticancer effects.

Laboratory experiments on arnica have shown that it can kill bacteria on contact, decrease inflammation, stimulate the respiratory system, and increase the force of heart contractions. However, these effects have only been seen in the laboratory setting, and it is not clear if arnica would have similar effects in humans. Arnica is often used in homeopathic medicine, in which extremely dilute solutions of botanicals and substances are taken by mouth. A few studies have shown that arnica may reduce symptoms of osteoarthritis. More research is needed.

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Purported Uses
  • To reduce swelling
    There is some evidence that arnica reduces swelling. More studies are needed.
  • To treat sprains and muscle pain following exercise
    Clinical trials do not support this use.
  • As a post-operative antibacterial agent
    Clinical trials do not support this use.
  • To reduce symptoms of osteoarthritis
    Arnica was shown in a few studies to be effective against osteoarthritis. More research is needed.
  • To reduce bruising
    One small study found that Arnica ointment was more effective for bruise healing than low concentration Vitamin K formulations.
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Research Evidence

Pain
Fifty-three subjects received two tubes of cream one containing arnica and the other containing placebo. The creams were applied to the right or left calf (as directed by labels on the tubes) immediately after exercise (calf raises), and again 24 and 48 hours post-exercise. Compared to the placebo group, pain increased in the arnica group after 24 hours. Pain scores were not significantly different at 48 and 72 hours post-exercise.

Bruise healing
This study involved 16 patients who had two bruises created on upper inner arms, by a pulsed dye laser. Four topical agents (5% vitamin K, 1% vitamin K/0.3% retinol, arnica, or white petrolatum) were randomly assigned to treat the bruises for 2 weeks. Improvement in bruise healing was greater for arnica than for white petrolatum or 1% vitamin K/0.3 retinol.

Osteoarthritis
This multicenter study included 204 outpatients with osteoarthritis. Patients were randomized to receive 5% topical ibuprofen or arnica gel 3 times daily for 3 weeks. Patients could also use acetaminophen tablets as a “rescue treatment” if pain was unbearable. Arnica was comparable in effectiveness to ibuprofen with respect to hand functional capacity, pain intensity, number of painful joints, duration and severity of morning stiffness, and acetaminophen intake.

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Patient Warnings
  • The F.D.A. considers arnica, when taken orally, an unsafe herb. External use appears to pose no risk.
  • Ingestion of arnica is not recommended. The effects of arnica on the lungs, heart, and uterus have not been sufficiently tested to justify the risks that are associated with taking this herb orally.
  • A fatal case of poisoning has been reported following ingestion of 70 g of arnica tincture.
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Do Not Take If
  • You are taking medication to lower your blood pressure (Arnica may lessen their effects).
  • You are taking warfarin or other blood thinners (Arnica may increase their effects).
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Side Effects
  • When taken orally: Gastrointestinal distress, tachycardia (abnormally fast heart rate), shortness of breath, coma, and death
  • When used topically: Contact dermatitis (redness and inflammation of the skin), burning
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Last updated: December 20, 2011
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