tea tree oil
Well, I think I've run my "control" experiment long enough. It does seem that my sinuses were less aggravated in general and for a shorter period of time when I was treating them with the tea tree oil last spring (a couple drops splashed on the shower wall so that the vapors are inhaled). I'm going to have to get some more soon to put an end to this (or at least to get it to back off somewhat).