Overview

Arnica (Arnica montana) is a plant whose flower is found in many homeopathic creams, lotions, and gels that are applied to the skin. It is also found in some homeopathic products that are taken by mouth. Arnica is commonly used for bruises, sprains, joint pain, or muscle pain, but its benefits are not well defined. Common side effects of applying arnica to your skin include itching, rash, redness, irritation, or dryness. Homeopathic arnica products are unlikely to cause side effects. But pure arnica can be toxic when taken by mouth. Before using arnica, make sure to tell your health care provider about any health conditions you have or medicines you are taking.

Uses

What is arnica used for?

Arnica (Arnica montana) is applied to the skin for many different reasons, including bruises, sprains, swelling, and joint or muscle pain. Arnica is also included in some homeopathic products that are taken by mouth. However, its benefits for any use are not well defined.

Note: The FDA has not reviewed arnica for safety and effectiveness, and it is not approved by the FDA. Learn more about homeopathic products here.

How does arnica work (mechanism of action)?

Arnica, also known as wolf’s bane, is a plant called Arnica montana. Products that contain arnica are usually made from the flowers of the plant. Arnica can be easily confused with a different plant (Heterotheca inuloides) that is known as Mexican arnica or false arnica. Mexican arnica is commonly used to make tea, and its effects and side effects are very different from those of arnica.

Most arnica products are homeopathic products. Homeopathic products are very dilute, which means they contain very small amounts of each ingredient. Sometimes, these amounts are so small that there may not be any arnica in the product at all. The very small amounts of arnica found in homeopathic products are unlikely to cause serious side effects. But pure arnica can be poisonous and cause serious side effects when taken by mouth or applied to your skin.

Homeopathic arnica has a long history of use for many skin-related conditions, as well as muscle and joint pain. Some people apply it to their skin, and other people take it by mouth. But it is not clear if or how arnica may work for any use.

Herbal products, such as arnica, naturally contain many different chemicals. The amounts of each chemical in a specific arnica product may vary. Some, none, or all of these chemicals may have effects on the body. These effects change depending on how much of each chemical is found in the product you are using.

How should I store arnica?

You should store arnica according to the product label. Most homeopathic products should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of arnica?

The most common side effects of arnica are listed below. These side effects may vary depending on how you are using arnica, the dose you are taking, or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

• Itching, rash, redness, irritation, or dryness (when applied to the skin, see below)
• Nausea, vomiting, diarrhea, or stomach pain (when taken by mouth)

There may be other side effects of arnica that are not listed here. Contact your health care provider if you think you are having a side effect. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of arnica?

While less common, the most serious side effects of arnica are described below, along with what to do if they happen.

Severe Allergic Reactions. Arnica may cause allergic reactions, which can be serious. Stop using arnica and get help right away if you have any of the following symptoms of a serious allergic reaction.

• Breathing problems or wheezing
• Racing heart
• Fever or general ill feeling
• Swollen lymph nodes
• Swelling of the face, lips, mouth, tongue, or throat
• Trouble swallowing or throat tightness
• Itching or skin rash
• Bumps on the skin called hives that can be red, pink, white, or brown, depending on your skin tone
• Nausea or vomiting
• Dizziness, feeling lightheaded, or fainting
• Stomach cramps
• Joint pain

Skin Reactions. Applying products that contain arnica to your skin can cause skin reactions, such as rashes, itching, and dryness. In some people, these skin reactions may be caused by an allergy to arnica (contact dermatitis). Stop using any products that contain arnica and contact your health care provider right away if you have a skin reaction.

Precautions

Who should not use arnica?

Allergies to Ingredients. People who are allergic to any of the following should not use arnica.

• Arnica (Arnica montana), also called Wolf’s bane
• Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific arnica products they stock.

What should I know about arnica before using it?

Pure arnica should not be swallowed or applied to the skin. It can be poisonous when swallowed and can also damage your mouth, throat, and stomach. Applying it to your skin can cause serious irritation or damage. Do not use products that contain pure arnica.

In the U.S., very small amounts of arnica may be added to foods for flavoring. Arnica may also be used in homeopathic products, which only contain very small amounts of each ingredient. These small amounts are unlikely to be poisonous or cause serious side effects. But some homeopathic products have been found to contain larger amounts than listed on the label. These large amounts can cause serious side effects. The FDA has not tested arnica products to confirm that they contain the ingredients or amounts stated on their labels. Learn more about the risks of homeopathic products here.

Read and follow the directions on the specific product you are using, or use it as recommended by your health care provider. Keep arnica out of the reach of children.

Small amounts of arnica may be added to homeopathic creams, gels, or lotions that are applied to the skin. Keep these products away from your mouth and eyes. If you get arnica in your eyes, wash them right away with water.

Do not apply products that contain arnica to damaged or broken skin, such as cuts, scrapes, or wounds. Do not bandage or wrap the area where you applied arnica unless your health care provider tells you to do so. Once you have placed a product that contains arnica on your skin, do not apply heat or ice for at least five minutes. If your symptoms get worse, stop using the product and tell your health care provider. If you are using arnica for a bruise or strain and it does not get better within three days, contact your health care provider.

Herbal products, such as arnica, naturally contain many different chemicals. The amount of each chemical in a specific arnica product can change for many reasons, including the area where the plant was grown, the weather during growth, the time of year when it was harvested, and the way that the plant was processed after it was harvested. If you switch to a new bottle or a different brand, you may not have the same effects or side effects because of this variability. Talk to your health care provider if you have questions or concerns.

What should I tell my health care provider before using arnica?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if arnica is right for you.

In particular, make sure that you discuss any of the following.

Allergies to Certain Plants.Arnica is part of the Asteraceae (daisy) family of plants. People who have an allergy to other plants in this family may be more likely to have an allergic reaction to arnica. Some examples of other common plants in the Asteraceae family include echinacea, marigold, chamomile, yarrow, ragweed, asters, and chrysanthemums. If you have an allergy to any of these plants, talk to your health care provider before using arnica.

Other Current and Past Health Conditions.Tell your health care provider if you have any of the following.

• Bleeding problems
• Upcoming surgery or other procedure

Other Medicines and Supplements.Arnica may interact with other medicines and supplements. Before taking arnica by mouth, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how arnica could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if arnica passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does arnica interact with foods or drinks?

There are no known interactions between arnica and foods or drinks.

It is unknown if drinking alcohol will affect arnica.

Does arnica interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking arnica by mouth.

• A blood thinner, which is a medicine used to treat or prevent blood clots
• Antiplatelet medicines, such as aspirin/dipyridamole, cilostazol, clopidogrel (Plavix), or ticagrelor (Brilinta), which are medicines used to prevent blood clots

The interactions between arnica and medicines are not fully understood. As with most homeopathic ingredients, the research on drug interactions with arnica is incomplete. Always check with your health care provider before using arnica with any medicines.

Dosing

What should I do if I accidentally use too much arnica?

If you or someone else has used too much arnica, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Arnica is available in many different forms, including homeopathic creams, lotions, and gels that are applied to the skin. Arnica is also available in homeopathic products that are taken by mouth. Read the product label closely and speak with a health care provider about how to use arnica safely. Do not use double or extra doses, even if you miss a dose.