I would suspect first, in the winter, mold/mildew -- including the foods list in link here. https://www.achooallergy.com/learning/mold-allergies-in-winter/ http

I would suspect first, in the winter, mold/mildew -- including the foods list in link here. https://www.achooallergy.com/learning/mold-allergies-in-winter/ https://www.achooallergy.com/learning/mold-allergies-in-wint... . Tho, i'm sure you tested for that as well... hope you find the trigger. I have also found that most typical minor "cold" symptoms for me stop immediately by taking Claritin D. I suspect its drying out things in the sinuses, and reducing some inflammation.