| Pain receptors that are activated by burning are indicating something harmful is occurring to your body not because the receptor is actually activated, but because of the cellular damage that triggers the receptor. On the other hand, capsaicin doesn't activate pain receptors by cellular damage. It activates pain receptors by allowing a flood of (Na+? Ca2+?) ions through cellular walls. This triggers the pain receptors to fire without the cell damage. That is a laymen's description of reference [1]. It's interesting because the biochemistry of spicy foods differs by the 'spicy' compound. Capsaicin isn't the only one at play, wasabi and horseradish-containing foods have an entirely different molecule responsible for producing the spicy sensation, allyl isothiocyanate.[2] If you're a fan of spicy peppers and horseradish, you have definitely noticed the difference in how the 'heat' manifests: capsaicin-containing foods cause areas of damaged skin or mucus membranes to feel painful, usually localized in the mouth or around nail beds of those preparing the peppers. Horseradish on the other hand, with it's spicy-ness provided by allyl isothiocyanate, produces a heat that - for me - is more located in the back of the head or in the upper sinus cavities. A completely different sensation than that of capsaicin. Unfortunately, I don't know what the biochemical method of action is to produce those feelings. I'm sure it is buried deep in the literature, but it isn't on the wiki. [1] https://en.wikipedia.org/wiki/Capsaicin#Mechanism_of_action [2] https://en.wikipedia.org/wiki/Allyl_isothiocyanate |