Spicy is pleasurable to me, but nothing beyond the 350K Scoville range. I can't even fathom 1M Scoville, not to speak of 5M+ Scoville. How do you recover from that?
The article prompted me to ask why our pain neurons interpret the capsaicin burn the approximately the same as a temperature burning sensation. It turns out we don't fully know yet [1]. Some spice hound is going to score big time doing graduate thesis work on answering this question, literally eating spicy food for science.
I though the article covered the question and was very informative: the only after-affect we've been able to show is the possible, eventual dulling of the pain neurons involved.
There's at least some concession to the title in the third to the last paragraph:
But, hours or a day or so of very serious discomfort aside, there don’t seem to be long-term dangers, per se, in eating very hot peppers. Biologists have observed, however, that administering capsaicin over long periods of time in young mammals does result in the death of the pain neurons, Bryant says. Setting the neurons off repeatedly wears them out, and they don’t grow back.
What sauces exist that at 5M+? If you're talking about pure capsaicin extract that you have added to your own food (essentially making your food into a sauce), then you aren't eating anything that is 5M SHUs, since that is not how the scale works.
Some of the Blairs brand of hot sauces claim up to 16 million on the scoville scale. I have tried the 4am sauce which claims 4M on the scoville scale, and it was not a laughing matter immediately, more crying, then laughing days later. (I love this stuff though, and would do it again!)
Having said that the stuff in the millions is pretty darn hard to find, they don't stock it or even sell it regularly.
Unfortunately, this article is almost completely devoid of real information, and doesn't answer the question at all.