What might be causing my allergies in the middle of winter?

I live in the Willamette valley in Oregon. (Eugene to be exact)This area is famed for terrible allergy’s. I believe I have allergy’s (and not a cold) but can’t figure out what is causing it. I am in the same house I have living for 4 years so its not household mold. I don’t see anything blooming so can figure out if its pollen. Can anyone please tell me What might be causing this allergy. Before this I have only had allergies in warly summer for a week or so. Maybe a recommendation of how to relieve symptoms without drugs.

Dust mites? That’s what gets to me.