Ya, tvashtarkatena has his head up his ass.
I haven't figured out what triggers mine. I've gotten it while long distance cycling in the summer heat of the south near sea level and winter climbing on Rainier. After that winter climb, I kept hacking for a month or so afterwards. Went to the doc and got an inhaler. Used it a few times on subsequent trips, and then quit. Haven't had an episode in the four years since.