Extract from the plant Arnica montana. There is research showing that when arnica is taken orally before surgery it reduces inflammation and reduces bruising (Source: Archives of Facial and Plastic Surgery, January–February 2006, pages 54–59). However, it is repeatedly stated in all herbal journals used for the compilation of this dictionary that arnica should not be applied to abraded skin because it is a significant skin irritant. The PDR Family Guide to Natural Medicines & Healing Therapies says: “Repeated contact with cosmetics containing arnica can cause itching, blisters, ulcers, and dead skin.” (Other Sources: IFA—International Federation of Aromatherapists; and www.int-fed-aromatherapy.co.uk).
Arnica also is associated with a high incidence of skin sensitization. It's bene shown to kill keratinocytes (skin cells) along with almost eliminating naturally-occuring defensive antioxidants present in skin (Sources: Sensors, June 2014, pages 11,293-11,307; and American Journal of Contact Dermatitis, June 1996, pages 94–99). Ironically, there's also research showing arnica extract's antioxidant ability can help protect fibroblasts (cells that make collagen) from damage, including oxidative damage from a substance like hydrogen peroxide (Source: Chemistry Central Journal, September 2012, pages 1-15).