I did notice tham that it happens when I am routing around in places that haven't been disturbed for a while like in the back of closets or under the bed or vacuuming and moving furniture to get under or in back of.
It doesn't happen while I am actually doing this stuff it's THAT night while I am sleeping.
Like whatever it is that flew up there needed some time to dig in and start tormenting me.
But then again, you could be around someone that is wearing something they had in the back of their closet.
One or two sessions with the NettiPot usually takes care of the problem. I can't do it twice in a row in each nostril, I have to wait a few hours to see if the first time got it.