I had cold 5 years ago and it laster for a month later on the ENT doctor told me it is sinusitis and then sinusitis is gone and i was diagnosed with allergic rhinitis. The mistery is that since I had the cold for 3 weeks until I ha've had the the allergy I ha've had brain fog. I think the main cause is the congestion/inflammation, i've been feeling nasal congested 24/7 for 5 years. Why my nose can't take a break from congestion even just for an hour but instead congested for 24/7 for 5 years. If it was allergy now then why I'm congested even though there's no allergens?