I have been unknowingly suffering from allergies for years. In the spring and fall I would suddenly become “sick” and nothing I did could get rid of it. It took years for me to discover that it was allergies, not a virus each time, because my allergy symptoms are identical to that of the flu (fatigue, sneezing, itchy throat etc.).
Eventually I figured that I may actually be suffering from allergies, and after taking allergy meds I started to feel much better. The only problem: allergy meds knock me out. Even non-drowsy options make me feel tired and weird. The solution: allergy shots (immonotherapy)!