I’m back from a scan of the Med Journals.
To quote the original question posed to Cecil as published in The Straight Dope:
Some people at work have offered me $10 to drink a two-ounce bottle of Tabasco sauce. Now I am having second thoughts. Is it dangerous, other than a few minutes of discomfort? . . ."
To which Cecil answered in part:
I certainly hope you like Gatorade and cough syrup, because that’s what you’re going to be living on for a week after you try this stupid stunt. The vegetable oils in Tabasco are fairly potent skin irritants. . . . At best your throat would hurt like hell for the rest of the evening; at worst you could end up with a mild chemical-type burn down the length of your esophagus. Admittedly the clinical literature on this topic is not as voluminous as one might like. . . ."
Cecil goes on to describe his efforts to make up for this deficiency by forcing a quart of Tabasco down one of the associate editors at SD HQ, unfortunately for science without success.
The frontiers of Tabasco research have advanced mightily since 1984, when The Straight Dope was published. As it turns out, the Master was not really incorrect, although the answer was perhaps a bit imprecise and the pain would probably not go on for a week.
The key receptor molecule, known as VR1 (from vanilloid receptor) can be triggered by damaging heat (over about 110 degrees F), acid (free protons), tissue inflammation, or capsaicin. The VR1 molecule naturally occurs only in the cell membranes of certain pain receptors (nociceptors), not ordinary cells. What happens is that channels are opened in the cell membrane which allow sodium and calcium ions to rush in, triggering nerve impulses that are perceived as pain. While heat and acid will also damage cells that are not pain receptors, capsaicin evidently will not.
However, that is not to say that there is no physical damage done by capsaicin. Too much calcium rushing in will kill the receptor cell. It seems to me that such cell death could itself provoke damage and inflammation in nearby tissues, but I have not yet found an article making a definite statement about this. This killing of receptor cells could in fact be described as “a mild chemical-type burn,” although a true chemical burn would also kill non-receptor cells.
This said, large doses of capsaicin that are insufficient to actually kill the receptor cell result in its eventual desensitization. Chili addicts know they can gradually withstand hotter and hotter dishes over time. And capsaicin preparations are actually used to reduce pain and inflammation due to this desensitizing effect, probably in conjunction with the production of endorphins.
I’m still looking into this and may have more later. In the meantime, here’s a fairly detailed if technical article on the receptor molecule:
www.nap.edu/books/0309065488/html/7658.html