Severe side effects that may occur when arnica is taken orallyorallyto be taken by mouth (swallowed) include:
- irritation of mucous membranes
- muscle weakness
- kidney damage
- liver damage
- rapid heart rate
- shortness of breath
- significant increase in blood pressure
- stomach pain
Arnica taken orally can also cause death.
Side effects that may occur after applying arnica topicallytopicallyto be applied on the skin include: itchiness, dry skin, and rash. Long term use of arnica on injured skin may cause eczema (a skin condition that involves painful red, itching, and oozing wounds), allergic skin reactions with pus containing blisters, and dead skin tissue.
Arnica can interact with some medications. It increases the effects of blood thinning medications (e.g., warfarin, heparin) and herbal products (e.g., angelica, clove, danshen, garlic, ginger, ginkgo, Panax ginseng, and other herbs), and blood clot dissolving medications (e.g., alteplase) and increases the risk of bleeding. If you are taking any of these medications or herbal products, consult your health care provider before using arnica.
If your symptoms persist or worsen after taking arnica, you should consult your health care provider. You should stop using arnica at least 2 weeks before surgery (to prevent any severe bleeding).
You should avoid taking arnica if you have any gastrointestinal (stomach and intestines) disease. You should also avoid taking arnica orally and applying it on broken skin, open wounds, mucous membranes, and eyes.
You should not take arnica if you are allergic to plants in the daisy/asteraceae/compositae family, such as ragweed, chrysanthemums ("mums"), marigolds, daisies, and others.
Do not use arnica if you are pregnant or breast-feeding. Consult your health care provider if you have any questions.
Before taking any new medications, including natural health products, speak to your physician, pharmacist, or other health care provider. Tell your health care provider about any natural health products you may be taking.