Answer on @Quora by @AdrianaHeguy to Why do we sweat when we eat spicy food? – Xochielt Sanchez
Answer by Adriana Heguy:
Spicy food contains capsaicin, which is the compound that gives spicy food its "heat". It's actually a fascinating bit of biology, as the capsaicin receptor, called(the Wikipedia link contains great information). This receptor did not evolve to bind capsaicin, but it's part of a series of nociceptors, or receptors for pain, that have a very important function, as practically all organisms must be able to detect harmful stimuli by feeling pain and retreating from the source of harm. TRPV1 is stimulated by temperatures above 43 degrees Celsius, and by acidic conditions, also by capsaicin and by the compound that gives mustard its pungency. When we eat spicy foods or mustard, we perceive the sensation as heat or "burn" and thus one of the possible reactions is sweating.