An agent which produces vaso-dilation of peripheral blood vessels by stimulating nerve-endings of the skin to generate irritation intended to relieve deep-seated pain. Arnica, Balm of Gilead, Black Mustard, Bryony (white), Cajuput (oil of), Camphor, Canada Balsam, Cayenne, Eucalyptus, Nutmeg (oil of), Sassafras, Thuja. ... counter irritant