Counterirritants

Counter-irritants, substances which produce irritation, and which are applied to the skin or other accessible parts, with the object of affecting deep-lying and inaccessible structures. For example, a poultice or blister is applied to the chest to relieve inflammation of the lungs or pericardium. Counter-irritation may act partly by drawing blood to the surface and so relieving congestion in the inflamed part, but probably its effect is mainly brought about through the nervous system.