Uses and Toxicity
Arnica montana is sometimes grown in herb gardens and has long been used medicinally. It contains the toxin helenalin, which can be poisonous if large amounts of the plant are eaten. It produces severe gastroenteritis and internal bleeding of the digestive tract if enough material is ingested. Contact with the plant can also cause skin irritation. The roots contain derivatives of thymol, which are used as fungicides and preservatives and may have some anti-inflammatory effect. When used topically in a gel at 50% concentration, Arnica montana was found to have the same effect when compared to a 5% ibuprofen gel for treating the symptoms of hand osteoarthritis.
A scientific study found that the application of topical arnica had no better effect than a placebo in the treatment of laser-induced bruising.
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