i did all the allergy tests, including food, all came back no allergy to anything. i know my phlegm is coming from my digestive system, the only time i get a so call post nasal thing is when it builds up for some reason which is why i use the navage to keep the sinuses clear...i have been reading and listening to videos from mayo and other medical places on how they now know that covid can mess up the good gut bacteria and just makes every thing a mess...they still are learning on this and still don't know how to fix it, we need to be patient..even as crappy frustrating as it is...they are working on it, this stinking evil virus is a big one, soooo we need to do our part best we can, i work at eating cleaner, the old common sense thing, we can get through this and i know even with a whole 35 long covid symptoms i have, i will not let this crap beat me, stay positive.....in two weeks it will be 4 years for me, i caught it on a flight to Montana...hugs to you all fighting this and to the people looking for a cure.........