I can think of a few immediate medical possibilities.
1. Risk of an allergic-type response whereby your esophagus closes and you can no longer breathe. I'm not sure an epi-pen would help with that either.
2. Nerve cell death
Now, some sources:
General Chemistry Online: Fire and SpiceHigh concentrations are toxic. Exposure is painful and even incapacitating. Capsaicin prevents nerve cells from communicating with each other by blocking the production of certain neurotransmitters; at high concentrations it destroys the cells.
It is an inflammatory, so obviously it's going to cause issues with eyes and that's what causes the suffocation effect. It's the same ingredient in pepper sprays, so it's not all too unlikely that hot sauce can have the same effect.
Consumer Basics Of Pepper Spray and MacePepper spray differs from mace in that it is an inflammatory product, not an irritant. Pepper spray causes the eyes to swell and the victim to immediately close them. Pepper spray causes airway inflammation,
Interestingly, it doesn't seem to make worse issues with ulcers (and may even help them):
Disease, Condition, & Injury Fact Sheets | NYU Langone Medical Centerintuitively, it seems that hot peppers should be hard on the stomach. However, remember that hot peppers don’t actually damage tissues—they merely produce sensations similar to those caused by actual damage. Apparently, by depleting substance P in the stomach, they reduce sensations of discomfort. In fact, some evidence suggests that oral use of cayenne or capsaicin can actually protect the stomach against ulcers caused by anti-inflammatory drugs . 5,6,7 However, contrary to some reports, cayenne does not appear to be able to kill Helicobacter pylori , the stomach bacteria implicated as a major cause of ulcers. 9
