On Food and Cooking

the calories that we do eat.
Of course there’s also capsaicin’s irritating
effects, which can be pleasurable in the mouth
but not necessarily elsewhere. (This is why
“pepper spray” is an effective weapon; it
makes breathing and seeing difficult for about
an hour.) Capsaicin is potent and oily and hard
to wash off surfaces, so small amounts left on
fingers can end up hours later being rubbed
into an eye. Knives, cutting boards, and hands
should be thoroughly washed with hot soapy
water to avoid this and similar unhappy
surprises. On the other hand, capsaicin
irritation has found a number of medical
applications; for example, when applied to the
skin it helps reduce muscle pain by increasing
local blood flow.