I didn't feel like looking up how to spell allyl isothiocyanate when writing my initial comment. Maybe I should have! I've edited it for clarity, since it's an important distinction which adds to why I'm so danged curious about the mechanism behind my friend's temporary inability to perceive pungency. I also see how my original wording may have implied I was conflating the two, so I've expanded on my friend's experience a bit. He experimented with pepper and radish based spice sources in his pantry.

But also, outside of Japan, 95% of the time the stuff with your sushi isn't wasabi, it's green-colored horseradish-and-mustard paste.