Its very mechanism, though, should remind us to be wary. As the North Carolina researchers point out, any compound that can influence nerve function is, by definition, risky. Research tells us that pepper spray acts as a potent inflammatory agent. It amplifies allergic sensitivities, it irritates and damages eyes, membranes, bronchial airways, the stomach lining – basically what it touches. It works by causing pain – and, as we know, pain is the body warning us of an injury.
On pepper spray. (via)