Thanks, I appreciate your informative response to a question I've had for awhile!
I offered a diagnosis months ago on this site re yeast causing runny nose. After reoccurence, I thought it out logically. OK, here it is. The bathroom is unique in relation to humidity as opposed to other rooms in your house. When steamy air expands, it go into your vents. Then mold forms from that moisture amount. You go to the bathroom and the furnace, A/C comes on and blows that mold on you! That mold will cause your nose to run and/or sneezing. I did this to stop it. Cut the vent off!! Stopped my problem. See if it works for you and spread the word if it is successful. Good Luck!