I had allergies for years. It was like a constant cold or worse - runny nose, itchy eyes, itchy throat, brain fog, fatigue, a little difficulty breathing (from being bunged up all the time), occasional tinnitus, etc. It was often a living hell. Often I couldn't exercise, because the extra breathing from exertion would make symptoms worse again. Symptoms would seem to go in cycles to an extent, but they never went away completely.

I went back and forth to doctors who were all useless. In the end, I tried cutting out various things in my diet. I was already vegan, which, by cutting out dairy, had reduced the symptoms for years, but I was still suffering from constant colds, just not as bunged up or run down as previously. I ended up finding that wheat was making everything worse. It took 5 weeks of not having any wheat at all (and before that. various other things) to find this out. Since then, I cut out all wheat, and hardly ever get cold like symptoms (or colds) any more, and never get hayfever any more. (The only time symptoms return is when I screw up and have wheat or spelt accidentally or thoughtlessly).

I found I'm also allergic to touching cardboard - I can't handle it without gloves or I'll get eczema, basically Having cardboard in the room where I sleep is a bad idea, and can set off itchy eyes and a slight sniffle. I'm also affected by damp and mold in a house, but less so since cutting out wheat.

I'm not saying everything is a wheat allergy, but it's definitely worth trying to isolate things. I found you need to completely cut something out of your diet for 5 to 6 weeks to notice if it's affecting you. Start with more common things or things you know to be bad.

Also, one year I suddenly starting getting allergic reactions to beer - pretty much any kind of beer brought on itchy, weeping eyes, sore throat, sneezing, etc. with symptoms lasting for hours. I talked to another guy who had the same thing happen in the same year, and we thought it might be to do with a change in yeast or sulphites or something that affected all brewers. I cut out beer, and years later cut out all alcohol.

I've found eating mostly organic food, cutting out cane sugar (and fructose syrup and similar), wheat, and alcohol has removed nearly everything that was making me ill for so long. It took a long time to find what worked for me, and doctors were absolutely no help at all. Pills and drugs only mask symptoms and don't deal with the root cause, and can often stop working after a while, depending on what's affecting you and how (this is what I'd found in the past, anyway). Diet and environment changes seem to have better long term results by far.

Food is grown as a commodity to make investors rich - a lot of it is literally poisonous; but it is possible in nearly every country to filter out the worst crap and get to healthier options. But look for changes in your environment, too - new paint in the house, a damp patch previously unnoticed, changed ingredients in laundry liquid/powder, new clothes, cat litter, etc. Something could be triggering all of this, and it can take some detective work to isolate it.

(And to answer expected questions about being a vegan who doesn't eat wheat or sugar or drink alcohol: I eat well, I eat plenty, and I have never felt healthier or better in ny life. But I do eat a wide range of fruit, veg, grains, beans, seeds, nuts, etc. and I mostly make my own food). And I'm not selling anyone veganism or a gluten free diet or anything else, just saying what worked for me when nothing else did.

Good luck, and I hope you find relief soon!