Common Names

  • Mountain tobacco
  • Leopard's bane
  • Wolf's bane
  • Mountain arnica

For Patients & Caregivers

How It Works

There is some evidence that arnica is effective in healing bruises and osteoarthritis. It has not been studied for any anticancer effects.

Laboratory experiments on arnica have shown that it can kill bacteria and decrease inflammation. However, it is not clear if the herb has similar effects in humans. A few studies have shown that topical arnica applied to affected areas may reduce symptoms of osteoarthritis and heal bruising. Arnica is often used in homeopathic formulas, in which extremely dilute solutions of botanicals and substances are taken by mouth. More research is needed to determine whether they are effective.

Purported Uses
  • To reduce bruising
    Studies on whether arnica can speed healing of bruises are mixed.
  • 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
    Arnica has antibacterial effects, but human data are lacking.
  • To reduce symptoms of osteoarthritis
    Arnica was shown in a few studies to be effective against osteoarthritis.


    Do Not Take If
    • You are taking warfarin or other blood thinners: Arnica may increase their effects. Clinical relevance is not known.
    • You are having surgery: In the lab, arnica has been shown to prevent the formation of clots. Clinical relevance is not known.
    • You are pregnant or nursing: Arnica tea ingested by one mother caused serious side effects in her breast-fed newborn.
    • You are allergic to sunflowers, marigolds, ragweed or other members of Asteracea family.
    Side Effects

    Case reports


    Oral, raw herb: Gastrointestinal distress, internal bleeding, rapid heartbeat, shortness of breath, and coma.
    Oral, homeopathic overdose: Severe vomiting followed by acute vision loss in both eyes after accidental overdose.
    Oral, infant exposure through breast-milk: Breakdown of red blood cells in a 9-day-old breastfed infant 48 hours after his mother began drinking arnica flower tea.
    Topical: Rash, skin inflammation at area of contact.

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    For Healthcare Professionals

    Scientific Name
    Arnica montana
    Clinical Summary

    Arnica is a perennial herb found in East Asia, Europe, the northern United States, and Canada. Its medicinal history dates back several centuries and arnica continues to be popular today. Its flowers and roots have been used to treat bruises, sprains, arthritic pain, and muscle aches. A highly diluted form of Arnica is also used in homeopathic remedies.

    In vitro studies show that arnica has antimicrobial (1) and anti-inflammatory (2) properties. A few clinical trials suggest that topical arnica is helpful for osteoarthritis (3) (4) (5), and significantly reduces bruising compared with placebo or low-concentration vitamin K ointments (6). However, a small study reported that topical arnica actually increased pain 24 hours after calf exercises (7).

    A systematic review of homeopathic arnica studies has previously considered their evidence of effectiveness to be insufficient (8). More recent studies report reduced postoperative swelling in patients following knee surgery (9), and reduced pain following tonsillectomy (10). Arnica may reduce bruising from rhinoplasty (20) (21), but was not helpful after blepharoplasty (22). Rigorous research is needed to determine the clinical benefits of homeopathic arnica.

    Purported Uses
    • Bruises
    • Inflammation
    • Sprains and Muscle pain
    • Infections
    • Osteoarthritis
    Mechanism of Action

    Sesquiterpene lactones, the active constituents in arnica, have anti-inflammatory properties and inhibit binding of transcription factors AP-1 and NF-κB to DNA (14). A tincture prepared from arnica flowers suppressed collagenase-1 (MMP1) and interstitial collagenase-13 (MMP13) mRNA levels in human articular chondrocytes in vitro (14). MMP13 and MMP1 enzymes are thought to play a significant role in cartilage and joint destruction and inflammation seen in osteoarthritis and rheumatoid arthritis. Both arnica tinctures and sesquiterpene lactones were found to suppress NF-κB activation and IL-12 production in dendritic cells at high concentrations, but can also have immunostimulatory effects when diluted (2). Another study found that sesquiterpene lactones inhibit platelet function by interacting with platelet sulfhydryl groups, probably associated with reduced phospholipase A2 activity (12). In addition to sesquiterpene lactones, the allergenic potential of arnica may be partly due to other allergens such as polyacetylenes (15).


    Pregnant and nursing women: Ingestion of arnica tea by a nursing mother caused serious side effects in a newborn (17).
    Allergies to sunflowers, marigolds, or ragweed: Individuals with allergies to members of the Asteracea family may likely be allergic to arnica.

    Adverse Reactions

    Case reports
    Oral, raw herb: Gastrointestinal distress, internal bleeding, tachycardia, dyspnea, and coma (11).
    Oral, homeopathic overdose: Severe vomiting followed by acute, bilateral vision loss after accidental overdose (18).
    Oral, infant exposure through breast-milk: Hemolytic anemia in a 9-day-old breastfed infant 48 hours after his mother began drinking an arnica flower tea (17).
    Topical: Contact dermatitis (8) (23).

    Herb-Drug Interactions

    Antiplatelet agents: Arnica inhibits platelet aggregation in vitro (12).
    Warfarin or other anticoagulants: Arnica may potentiate their effects (19).

    Clinical relevance of these interactions is not known.

    Dosage (OneMSK Only)
    1. Iauk L, Lo Bue AM, Milazzo I, et al. Antibacterial activity of medicinal plant extracts against periodontopathic bacteria. Phytother Res. Jun 2003;17(6):599-604.
    2. Lass C, Vocanson M, Wagner S, et al. Anti-inflammatory and immune-regulatory mechanisms prevent contact hypersensitivity to Arnica montana L. Exp Dermatol. Oct 2008;17(10):849-857.
    3. Knuesel O, Weber M, Suter A. Arnica montana gel in osteoarthritis of the knee: an open, multicenter clinical trial. Adv Ther. Sep-Oct 2002;19(5):209-218.
    4. Widrig R, Suter A, Saller R, et al. Choosing between NSAID and arnica for topical treatment of hand osteoarthritis in a randomised, double-blind study. Rheumatol Int. Apr 2007;27(6):585-591.
    5. Ross SM. Osteoarthritis: a proprietary Arnica gel is found to be as effective as ibuprofen gel in osteoarthritis of the hands. Holist Nurs Pract. Jul-Aug 2008;22(4):237-239.
    6. Leu S, Havey J, White LE, et al. Accelerated resolution of laser-induced bruising with topical 20% arnica: a rater-blinded randomized controlled trial. Br J Dermatol. Sep 2010;163(3):557-563.
    7. Adkison JD, Bauer DW, Chang T. The effect of topical arnica on muscle pain. Ann Pharmacother. Oct 2010;44(10):1579-1584.
    8. Ernst E, Pittler MH. Efficacy of homeopathic arnica: a systematic review of placebo-controlled clinical trials. Arch Surg. Nov 1998;133(11):1187-1190.
    9. Brinkhaus B, Wilkens JM, Ludtke R, et al. Homeopathic arnica therapy in patients receiving knee surgery: results of three randomised double-blind trials. Complement Ther Med. Dec 2006;14(4):237-246.
    10. Robertson A, Suryanarayanan R, Banerjee A. Homeopathic Arnica montana for post-tonsillectomy analgesia: a randomised placebo control trial. Homeopathy. Jan 2007;96(1):17-21.
    11. Dinman S. Arnica. Plast Surg Nurs. Jan-Mar 2007;27(1):52-53.
    12. Schroder H, Losche W, Strobach H, et al. Helenalin and 11 alpha,13-dihydrohelenalin, two constituents from Arnica montana L., inhibit human platelet function via thiol-dependent pathways. Thromb Res. Mar 15 1990;57(6):839-845.
    13. Schulte KE, Rucker G. [Polyacetylenes and some other new contents of Arnica blossoms]. Arch Pharm Ber Dtsch Pharm Ges. May 1966;299(5):468-480.
    14. Jager C, Hrenn A, Zwingmann J, et al. 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. Oct 2009;75(12):1319-1325.
    15. Salapovic H, Geier J, Reznicek G. Quantification of Sesquiterpene Lactones in Asteraceae Plant Extracts: Evaluation of their Allergenic Potential. Sci Pharm. 2013;81(3):807-818.
    16. Hausen BM.FDA Poisonous Plant Database. 1980. Accessed February 17, 2020.
    17. Miller AD, Ly BT, Clark RF. Neonatal hemolysis associated with nursing mother ingestion of arnica tea. Abstracts of the 2009 North American Congress of Clinical Toxicology Annual Meeting, September 21–26, 2009, San Antonio, Texas, USA [abstr. 120]. Clinical Toxicology. 2009;47:726.
    18. Venkatramani DV, Goel S, Ratra V, et al. Toxic optic neuropathy following ingestion of homeopathic medication Arnica-30. Cutan Ocul Toxicol. Mar 2013;32(1):95-97.
    19. Heck AM, DeWitt BA, Lukes AL. Potential interactions between alternative therapies and warfarin. Am J Health Syst Pharm. Jul 1 2000;57(13):1221-1227; quiz 1228-1230.
    20. Simsek G, Sari E, Kilic R, et al. Topical Application of Arnica and Mucopolysaccharide Polysulfate Attenuates Periorbital Edema and Ecchymosis in Open Rhinoplasty: A Randomized Controlled Clinical Study. Plast Reconstr Surg. Mar 2016;137(3):530e-535e.
    21. Chaiet SR, Marcus BC. Perioperative Arnica montana for Reduction of Ecchymosis in Rhinoplasty Surgery. Ann Plast Surg. May 2016;76(5):477-482.
    22. van Exsel DC, Pool SM, van Uchelen JH, et al. Arnica Ointment 10% Does Not Improve Upper Blepharoplasty Outcome: A Randomized, Placebo-Controlled Trial. Plast Reconstr Surg. Jul 2016;138(1):66-73.
    23. Cercal Fucci-da-Costa AP, Reich Camasmie H. Drug Delivery After Microneedling: Report of an Adverse Reaction. Dermatol Surg. 2018 Apr;44(4):593-594.
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