Arnica is a genus of perennial herbs belonging to the sunflower family (Asteraceae). Several species of Arnica, mostly notably A. montana, contain an anti-inflammatory compound believed to relieve pain, aches, and bruising when applied topically.
|Verywell / Anastasia Tretiak|
Arnica is indigenous to sub-alpine regions of western North America but can also be found in arctic regions of Europe, Asia, and North America.1
Arnica plants have long downy leaves and bright yellow or orange daisy-like blossoms between two and three inches wide.
Helenalin, the ingredient that is believed to give arnica its anti-inflammatory effects,2 is extremely toxic when consumed and irritating to the skin unless diluted.
Arnica is most commonly sold as an over-the-counter topical ointment, gel, or cream or homeopathic preparation (topical application or oral pellet) and may be found as an extract, tincture, oral supplement, powder, aromatherapy oil, and dried “wild-crafted” herb.
Arnica is commonly used in alternative medicine for treating bruising, pain, myalgia (muscle soreness), and arthralgia (joint aches). Because the plant can be toxic, it is most often used in a homeopathic form.
Arnica is commonly marketed by homeopathic drug manufacturers as an effective treatment for:
However, only limited scientific evidence supports its use in treating any medical condition.2
That’s not to say arnica is without benefits; it’s simply that clinical studies investigating arnica are almost invariably small, poorly designed, and often contradictory in their findings.
It’s important to speak with a doctor to determine if arnica is a reasonable and safe option to explore either on its own or along with other pain medications.
Osteoarthritis, often referred to as “wear-and-tear” arthritis, is generally treated with nonsteroidal anti-inflammatory drugs (NSAIDs).
Proponents of arnica have long suggested that arnica has anti-inflammatory properties that offer a reasonable and safe natural alternative to NSAIDs.
In a review published in the Cochrane Database of Systematic Reviews, Australian researchers analyzed seven previously published trials on the benefits of topical herbal remedies for osteoarthritis.3
Of the remedies studied, arnica gel appeared to work nearly as well as Advil (ibuprofen) in reducing pain and improving joint function in people with hand osteoarthritis.
However, people who used arnica gel had a higher incidence of side effects compared to Advil (13% versus 8%), and some even reported an increase in joint stiffness and pain.
Post-Surgical Pain and Bruising
Proponents of arnica believe that it can reduce bruising and swelling following surgery when applied topically or taken as an oral supplement.
A 2016 review of studies in the American Journal of Therapeutics suggested that A. montana was a “valid alternative” to nonsteroidal anti-inflammatory drugs in treating:
- Post-operative pain
- Edema (swelling)
- Ecchymosis (bruising)
Reviewers did state, though, that the results varied substantially by the formulation, dosage, and study.4
By contrast, another review published in Dermatologic Surgery found insufficient evidence to support the use of oral or topical arnica in treating post-surgical swelling or bruising.5
Myalgia (muscle pain) is associated with a wide range of medical conditions as well as the simple overuse of your muscles.
Most studies investigating arnica have focused on its use in treating post-exertional myalgia. Arnica has long been used in sports supplements for this purpose, even though there is little evidence to support such use.
A highly subjective review of studies in the International Journal of Complementary and Alternative Medicine strongly endorsed the combined use of oral and topical arnica in treating muscle injuries even though four studies included in the review found no benefits compared to a placebo.6
Possible Side Effects
Arnica, in herbal preparations, is known to cause side effects even when used in highly diluted topical preparations. More serious side effects can occur with oral forms.
In non-homeopathic preparations, arnica may cause a mild allergic reaction, most notably in people with a pre-existing allergy to plants of the Asteraceae family, including ragweed, marigolds, chrysanthemums, and daisies.7
Arnica can also trigger transient increases in blood pressure and heart rate, particularly if used excessively or on broken skin.1 Broken skin allows for greater absorption of the active ingredient and may also cause localized stinging.
Most homeopathic arnica remedies are extremely diluted and considered safe. However, some forms may contain detectable amounts of helenalin which may pose health risks.
When taken by mouth, detectable amounts of helenalin can cause:1
- Mouth and throat irritation
- Stomach pain
- Shortness of breath
- Easy bruising and bleeding
- Rapid heartbeat
- High blood pressure
Oral preparations containing pure arnica should be avoided without exception. Not only are they more likely to cause symptoms, but they can also damage the heart and increase the risk of organ failure, coma, and death.8
Contraindications and Interactions
Theoretically, arnica could slow blood clotting, and any non-homeopathic preparations of arnica should be discontinued two weeks prior to surgery to reduce the risk of post-operative bleeding.
Similarly, arnica should be avoided if you are taking any anticoagulant (blood-thinning) drugs because the combination could theoretically increase your risk of bleeding and bruising.
These drugs include:
- Coumadin (warfarin)
- Plavix (clopidogrel)
- NSAIDs (e.g., anti-inflammatories like ibuprofen and naproxen)
Little is known about the safety of arnica during pregnancy. If you are pregnant or breastfeeding, consult your doctor before using arnica in any form.
|Verywell / Anastasiia Tretiak|
Selection, Preparation, and Storage
Arnica montana is the species most commonly used for medicinal purposes, although chamissonis, A. longifolia, and A. gracilis are also sometimes used.
Most over-the-counter arnica preparations are sold as homeopathic preparations or are repeatedly distilled, resulting in gels, ointments, and extracts with little to no helenalin. The same applies to arnica powders, capsules, and sublingual pellets that typically contain no helenalin.
When purchasing arnica, look for brands that have been tested by an independent certifying body like the:
- U.S. Pharmacopeia (USP)
- NSF International
This way, you can be sure the ingredients on the product label are correct and tell if any helenalin is included in the formulation.
You should also check that the Latin name of the arnica species (such as Arnica montana) is included on the product label, and be wary of any product that claims to contain “pure arnica.”
Never buy dried wild-crafted arnica or grow fresh arnica to make teas or tonics. There is no way to dose preparations like these, and your exposure to helenalin is likely to be excessive, if not dangerous.
Most arnica preparations can be stored at room temperature. As a general rule, store them in their original containers away from direct sunlight and never use more than the dose listed on the product label. Discard any preparation that is past its expiration date.
A Word From Verywell
Because herbal remedies are not subject to the same regulatory standards applied to pharmaceutical drugs, be cautious when using any such product and speak to your doctor first if you are thinking about trying one.
Remember that even natural products can be dangerous, cause unwanted side effects, and have negative interactions with other drugs or supplements you’re taking.
Kriplani P, Guarve K, Baghael US. Arnica montana L. – a plant of healing: Review. J Pharm Pharmacol. 2017;69(8):925-45. doi:10.1111/jphp.12724
Jakobs A, Steinmann S, Henrich SM, Schmidt TJ, Klempnauer KH. Helenalin acetate, a natural sesquiterpene lactone with anti-inflammatory and anti-cancer activity, disrupts the cooperation of CCAAT box/enhancer-binding protein β (C/EBPβ) and co-activator p300. J Biol Chem. 2016;291(50):26098-108. doi:10.1074/jbc.M116.748129
Cameron M, Chrubasik S. Topical herbal therapies for treating osteoarthritis. Cochrane Database Syst Rev. 2013;(5):CD010538. doi:10.1002/14651858.CD010538
Iannitti T, Morales-Medina JC, Bellavite P, Rottigni V, Palmieri B. Effectiveness and safety of Arnica montana in post-surgical setting. Pain and Inflammation. Am J Ther. 2016;23(1):e184-97. doi:10.1097/MJT.0000000000000036
Ho D, Jagdeo J, Waldorf HA. Is there a role for arnica and bromelain in prevention of post-procedure ecchymosis or edema? A systematic review of the literature. Dermatol Surg. 2016;42(4):445-63. doi:10.1097/DSS.0000000000000701
Charlton F. Let’s set the record straight! Traumatic tissue injury treated with homeopathic Arnica montana – A Injury therapists perspective. Int J Complement Alt Med. 2015;1(5):00032. doi:10.15406/ijcam.2015.01.00032
Denisow-Pietrzyk M, Pietrzyk Ł, Denisow B. Asteraceae species as potential environmental factors of allergy. Environ Sci Pollut Res Int. 2019;26(7):6290-300. doi:10.1007/s11356-019-04146-w
Memorial Sloan Kettering Cancer Center. Arnica. Updated March 6, 2018.
Kriplani P, Guarve K, Baghael US. Arnica montana l . – a plant of healing: review. Journal of Pharmacy and Pharmacology. 2017;69(8):925-945. doi:10.1111/jphp.12724
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