now I do! Wiki doesn't say sneezing is a symptom, though, and that is the one symptom Our Hero unambiguously canonically has. so.

anaraine guesses bird dander, and poking at that further, WebMD suggests bird dander or mites (which may or may not be the same type that one would find in down feather bedding, I haven't poked that yet); I suspect bird dander is the route I'm taking.

thanks!