Other common name(s): arnica root, common arnica, arnica flowers, mountain arnica, mountain tobacco, leopardsbane, wolfsbane
Scientific/medical name(s): Arnica montana
Arnica is a perennial herb that grows in Europe, the northern United States, Canada, and eastern Asia. Its daisy-like flower and root, or rhizome, are often used in herbal medicines.
This herbal remedy is used on the skin for wounds, infections, and inflammation. It also is used to prepare a homeopathic medicine (see "Homeopathy"). Available scientific evidence does not support most of the claims about arnica's effectiveness.
If the herb is taken by mouth, it can be poisonous. It has caused a number of serious reactions, including allergies and at least one death.
How is it promoted for use?
Arnica is promoted for use on the skin to help soothe and heal wounds, sunburn, bruises, sprains, sore muscles, irritation from accidental injuries and burns, arthritis, ulcers, acne, eczema, chapped lips, sore throat, and irritated nostrils. Arnica contains organic chemicals such as sesquiterpene lactones and flavonoid glycosides that are claimed to reduce the swelling, redness, and pain linked to inflammation. It is also touted to help heal bacterial infections.
The herb is not usually recommended for internal use because it can irritate the stomach and may cause vomiting, diarrhea, and nosebleeds. Some homeopathic practitioners claim that a very diluted solution can be taken by mouth to treat low-grade fevers, colds, bronchitis, seasickness, inflammation of the mouth and throat, and epilepsy. (See our document, Homeopathy.)
Germany's Commission E has approved arnica only for use on the skin in treating injury and effects of accidents, inflammation of the mouth and throat area, and insect bites. It is considered unsafe for internal use.
Arnica is also an ingredient in some herbal skin care products and shampoos.
What does it involve?
Arnica is used as a whole or cut herb, powder, tea, liquid, gel, cream, ointment, oil, tincture, spray, or salve. The herb can be soaked with water and made into a poultice (a soft, moist mass of herbs) that is placed directly on the skin. Arnica ointments usually contain up to 15% of arnica oil or 25% of a tincture of arnica (the herb mixed with alcohol). Blistering and inflammation may be more likely if very strong solutions are used on the skin.
Homeopathic liquids reportedly contain little or no actual arnica and are usually placed under the tongue. Homeopathic tablets are also reported to contain extremely small or undetectable amounts of arnica, but the dose may vary.
What is the history behind it?
Herbal medicines made from arnica flowers and roots have been popular for hundreds of years. It has been said that the German poet and philosopher, Goethe (1749-1832), drank arnica tea to relieve chest pains. In some cases, the leaves may have been smoked, like tobacco. More recently, homeopathic and topical uses have been emphasized, mainly due to the possible harm in taking the herb by mouth.
What is the evidence?
Available scientific evidence does not support most of the claims about arnica's effectiveness. A 1998 review in the Archives of Surgery looked at 8 controlled human trials of arnica, and found that arnica worked no better in treating injuries than the placebo with which it was compared. The authors found that the studies they reviewed had serious flaws in the methods used to evaluate the effectiveness of arnica. They concluded that the human trials did not show that arnica was helpful or beneficial. One randomized clinical trial actually found that arnica appeared to increase pain and cause more swelling than the placebo in patients who had their wisdom teeth removed.
A 2003 study of 62 patients tested homeopathic arnica to find out whether it reduced pain and bruising in patients having surgery for carpal tunnel syndrome. There were no differences in pain or bruising between the arnica and placebo groups.
A double-blind, randomized British study of 37 patients looked at homeopathic arnica in tablet and ointment form to learn whether it helped people having surgery for carpal tunnel syndrome. A week after surgery, there were no differences in grip strength, wrist swelling, or pain between the group that was given arnica and the placebo group. Two weeks after surgery, the group that had arnica reported somewhat less pain than the other group, although there were still no differences in grip strength or swelling. Further studies are needed to find out whether this one difference is due to chance or to the effects of the arnica.
In 2002, a small Miami study looked at arnica gel to see whether it would reduce bruising after laser surgery to the face. No difference in bruising was noted between the patients who used plain gel and those who used the arnica gel.
In 2006, German researchers analyzed 3 studies on the use of arnica after knee surgery. Homeopathic arnica was given before and after surgery in all 3 studies. There were no significant differences in swelling after surgery between the arnica groups and the placebo groups in 2 out of 3 of the studies.
A 2007 controlled study looked at homeopathic arnica in patients who had their tonsils removed. One group received arnica and the other a placebo. Patients were surveyed afterward, with 111 out of 190 patients returning their questionnaires. The arnica group reported slightly lower pain levels than the placebo group, although there was no difference in how much pain medicine they needed, the period of time before they went back to work, and the number of visits they made to the doctor afterward. There was also no difference between the groups in bleeding and infection after surgery. A similar outcome was observed in a study published in 2010, in which patients got a mixture of arnica along with another homeopathic remedy after heart valve surgery. There was no difference between the placebo and homeopathic arnica groups in terms of blood loss, pain, fever, or lab results.
A toxicology assessment completed in 2001 concluded that there was not enough safety information on arnica to support allowing its use in cosmetics.
One 1994 study found that some of the chemicals extracted from arnica can kill colon and lung cancer cells growing in laboratory dishes. No follow-up studies in animals or humans have been published since then, possibly due to the side effects that can happen when arnica is taken internally.
Several laboratory studies suggest that arnica may reduce the activity of certain types of immune system cells. However, much more research in animals and humans would be needed to find out whether this effect is helpful or harmful to people with cancer or other diseases.
Are there any possible problems or complications?
Small, single doses of the herb are considered safe to use on the skin. Repeated use can cause skin reactions, severe inflammation, itching, blisters, skin ulcers, and other allergy-related skin problems. Use of very concentrated herb on the skin can increase the risk of irritation. Using the drug on broken skin or mucous membranes can irritate and increase the risk of more serious reactions.
Internal use is not recommended because arnica may cause vomiting, diarrhea, internal bleeding, rapid heartbeat, muscle weakness, nervousness, nosebleeds, and coma. At least one death has been reported. Arnica may reduce the effectiveness of medicines for high blood pressure and increase the risk of bleeding in people who take blood-thinning medications. People taking medicines that affect the heart's rhythm or function may have more serious effects from arnica.
People who are allergic to arnica may suffer runny nose, itching, hives, shortness of breath, and shock. Those with allergies to other members of the plant family Asteraceae, such as sunflowers, echinacea, marigolds, chamomile, or ragweed may be more likely to be allergic to arnica.
Effects on pregnant women and children are not well known. Women who are pregnant or breast-feeding should not use this herb. Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.
More information from your American Cancer Society
The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-227-2345).
American Cancer Society Operational Statement on Complementary and Alternative Methods of Cancer Management
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Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.
Last Revised: 08/09/2010