The oil obtained from the dried flower heads of the arnica, Arnica Montana, infused in rice bran oil in the ratio of herb:oil 1:5 General Description Arnica Infused Oil. For life's little bumps. Arnica grows in woods and pastures in central Europe, Siberia and the U.S. and Canada, and has been used extensively in European Folk Medicine. For external use only. Do not apply to broken skin. Historical Background Arnica has been used traditionally to ease bumps, bruises and sprains.