So what exactly causes the burning sensation of peppers? And if the chemical that causes the burning sensation is some sort of defense mechanism, then why does it taste so good! Along these same lines, why do some liquids, such as water, soothe the burn more than others, such as coke? And since we’re talking about the burning sensation…why do they burn your rectum upon exiting the body?
The chemical in all hot peppers is capsaicin. (http://www.thinkgeek.com/tshirts/generic/3813/)
I’ve read that it is indeed a defense mechanism, and in fact humans are the only animals “preverted” enough to like it! And I’m one that really does like it.
Thank you for the fast response, citizen. I will look over this article you have provided.
The chemical is not water based. It’s an oil.
This is why milk, for example, is better at quenching the fire than water. Milk adheres to your mucous membranes and mixes with the oil, making it easier to remove with the next gulp. Water simply runs off the oily coat the stuff puts on the inside of your mouth, washing off SOME of the stuff, but leaving the rest embedded in the crevices between your taste buds and suchlike.
Not quite. Birds are completely unaffected by oleoresin capsaicin, and they are the primary dispersers of pepper seeds. If most other animals ate them, their digestive tracts woudl destroy the seeds, but they pass right through birds unharmed.
That makes complete sense. Thanks for the response guys! I’m going to assume that the chemical that causes the burn is not broken down in the digestive system, therefore burns the anus upon exiting.
There’s several sites on the web describing and/or selling hot sauces, you might find interesting. The hotter ones have chili extract or pure capsaicin as ingrediants, making them hot enough to vaporize a yak.
Here’s one:
http://www.chez-williams.com/Hot%20Sauce/hothome.htm
But Q.E.D., the birds don’t enjoy it, which was my point. 
They still sell that shirt?? I want…
Oh wait, it says out of stock. Dangit.
Capsaicin isn’t the whole story here. Peppers produce a variety of substances, called capsaicinoids, that contribute to their heat. Most of the zing comes from capsaicin and dihydrocapsaicin, but the minor components; Homocapsaicin, Homodihydrocapsaicin, Nordihydrocapsaicin etc. all contribute their own unique pungency. The relative proportions of the various compounds changes during pepper ripening which explains the not so subtle differences in flavor between a storebought green jalapeno, and a bush-ripened red death-pepper.
Squink, nice links! Got any data on the Guatemalan insanity pepper? 
I’m too old for that hallucinogenic stuff anymore, so I stick with the home-canned sweet habanero relish. A little dab’ll do ya ! 
Every try habanero jelly? I bought a jar once in Palm Desert. It was delicious!
Oh Yeah! There’s a local company that makes the stuff. It’s perfect for a szechuany sweet and sour dish.
While we’re on the subject, Wilbur Scoville designed the heat scale for peppers. Now it’s done by chemical analysis, but he did it by taste: dilute the pepper with water until it doesn’t burn, and the level of dilution is your rating.
Scoville’s picture used to be up on the Web somewhere, but Google doesn’t find it. Can anybody steer me to one?
The subject of neurally mediated pain and subclinical euphoria is complex, and I haven’t researched it thoroughly, but there are severall suggestive facts, e.g.
Type II alpha-delta fibers [which signal pain at temperatures greater than 43C] have a temperature sensitive ion-gate channel protein (basically a temperature sensor molecule) called TRPV1 or VR1 which is also activated by capsaicin. Special mice whose TRPV1 gene has been knocked out do not avoid capsaicin solutions, and have a blunted response to what would normally be painful heat. Birds have TRPV1 receptors which respond to heat (and acids), but do not respond to capsaicin; they happily eat hot chili peppers and disperse the seeds., but as you note, they don’t enjoy it, possibly because their TRPV1 isn’t susceptible to it.
Capsaicin is used topically (applied to the skin) to counteract pain, even though it acts as an irritant. You can buy dilute ointments sover he counter, but it’s also used by pain specialists in solutions so strong that the doctor must wear protection when applying it.
I realize that there’s a leap between relieving pain and actual enjoymen, but I think that if you google “Substance P” (an important agent in somee pain pathways) and capsaicin together, you’ll find far more neurological info than I can recall at this hour of the night.
More information on birds and peppers can be found in my Staff Report:
Are birds immune to hot pepper, enabling them to eat vast amounts and spread the seeds?
SD Staff George
SD Science Advisory Board
Has anyone besides me eaten raw chili peppers? They’re not hot. They get spicy when you cook them. Since wild animals don’t roast their peppers first, the seed dispersal theory doesn’t hold water.
Nicely done!