Arnica is a perennial herb cultivated by homeopathic practitioners as a remedy to treat bruises, sprains, boils and rashes. Though there are no standard strengths for the arnica tablet, the 30x dilution strength — meaning one part pure arnica in 10 parts diluent, diluted 30 times — is commonly sold. Dosage varies depending on the severity of the injury, and there are several contraindications associated with arnica tablets.
Proponents of arnica believe that taking arnica tablets can help to counter the effects of tissue damage by stimulating white blood cells to help disperse blood around damaged tissue. The FDA recognizes arnica as an homeopathic active ingredient, but because it is a dietary supplement, it does not require FDA approval. According to the American Cancer Society, the healing effects of arnica have not been confirmed by scientific evidence, and the herb in its pure form is considered poisonous if taken by mouth.
Arnica tablets can cause vomiting, diarrhea, stomach pain, skin rashes, accelerated heartbeat, increased blood pressure and heart damage. Women who are pregnant or breast-feeding should not take arnica, and people allergic to ragweed and other related plants should check with their health care provider before taking arnica tablets. In addition, people with Crohn’s disease or irritable bowel syndrome should not take arnica because of its effects on the digestive system.
Arnica tablets may interact with anticoagulant and antiplatelet drugs that slow blood clotting. Arnica may slow blood clotting, which could lead to an increase of bleeding and bruising. Medications that slow blood clotting include ibuprofen, aspirin and naproxen.
Overdose symptoms may include mouth irritation, itching and swelling of the face, tongue and throat, dizziness and shortness of breath. People experiencing any of these symptoms when taking arnica should contact their physician.