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Arnica is an herb that grows in Europe and the U.S. It’s often used as a skin treatment for bruises, aches, and pains.

Arnica Uses

Some lab experiments suggest that arnica might kill bacteria and ease swelling. But the effects in people aren’t clear.

Studies of topical arnica gels and ointments for bruising and arthritis symptoms -- like pain and swelling -- have had unclear results. So far, research suggests that arnica skin treatments don’t ease muscle pain.

If eaten, the actual herb is toxic and can be fatal. However, some oral supplements contain highly diluted arnica. These are considered homeopathic treatments. These low-dose arnica tablets are safe to use and have been studied for blood clots, diarrhea, diabetic eye damage, and swelling and pain after surgery. More research needs to be done to establish effectiveness for those problems. A study of children with cancer, however, found that homeopathic low-dose arnica may help reduce mouth ulcers related to chemotherapy.

Because of the risks of pure arnica, the FDA classifies it as an unsafe herb.  Doctors who practice complementary medicine generally advise against using arnica in any form other than in a highly diluted homeopathic form.

Arnica Dose & Instructions for Use

Since arnica is an unproven treatment, there is no clear advice on how to use it. Given its risks, talk to a doctor or pharmacist before taking arnica orally.

Arnica Food Sources

There are no natural food sources of arnica besides the plant itself. Arnica is used as a flavoring in some food products.

Arnica Supplement Information

Arnica can come in tablets, tinctures, ointments, gels, and mouth rinses. Like any supplement, keep arnica in a cool, dry place, away from humidity and direct sunlight.

Arnica Warnings

  • Side effects. Pure arnica herb is poisonous. Homeopathic doses are generally considered safe to use. Arnica creams or gels can cause burning and skin irritation. Arnica can trigger allergic reactions in some people. Your risk may be higher if you also have allergies to plants like ragweed, daisies, marigolds, or chrysanthemums. 
  • Risks. Always talk to a doctor before using arnica. When swallowed, pure arnica can cause rapid heartbeat, gastrointestinal problems, kidney and liver damage, coma, and death. Don’t use undiluted arnica topically on broken or sensitive skin.
  • Interactions. If you take any medicines regularly, discuss them with your doctor before you start using arnica supplements. They could interact with drugs like painkillers, steroids, blood pressure drugs, blood thinners, and herbs like ginkgo biloba, garlic, and saw palmetto.

Given the lack of evidence about its safety, arnica is not recommended for children or for women who are pregnant or breastfeeding.

WebMD Medical Reference

Reviewed by Kimball Johnson, MD on June 27, 2012

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