This is a dust mite:
I had a sinus infection for most of the period 2008-2010 ... finally started changing my pillowcases every couple of days and got rid of it.
But this winter I started another one, lasting for a couple of months and ongoing.
My go-to fix for any runny nose problem has been
This works well, but caused my first (of my life):
Yep, a nosebleed. So no more Zyrtec.
I visited my "primary care team" and got diagnosed with "rhinitis" (a sinus problem that they don't know the cause of) ... and got supplied with (1) Claritin (works a bit for 3 hours tops) ... was offered Flonase, but major risk factor was nosebleeds so no thanks. Then was prescribed an antibiotic with no extra exam to find out if the sinus problem was bacterial or what ... I took a course of them; no difference.
Finally got onto the Modern Nose Clinic in Bellevue WA, which (a) did a CT Scan of my nose (pretty clear, just a little snurfling) and scheduled an allergy test for the next week.
I got the allergy test, where they put these plastic grids of slightly sharp delivery blobs of allergen into your arms.
I got my allergy report today, and despite a little technology glitch getting the report to me, I got results that didn't (mostly) surprise me:
Focusing on the dust mites, the solution:
Make sure you have 3 sets of bedding (including the pillowcases); put the one you take off your bed first in the freezer.
Then when you take it out of the freezer, wash the set in very hot water:
Dry that one and keep one fresh one on the bed, the latest off the bed in the freezer, and one folded on the shelf and ready.
Also remove any throw pillows, Teddy Bears, etc. from your bedroom:
And no more dust mites so you can breathe freely!