D.B.
A food "allergy" or sensitivity is an auto-immune response, where your body assumes that a harmless ingredient or environmental object/particle is harmful. So it mounts a huge defense to get rid of it. But what's really happening is your body lacks what it needs to effectively manage or process that trigger. You seem to have that with a variety of triggers - maybe it's soy (processed, possibly GMO, washed with things like hexane and alcohol most likely), but you also have outdoor allergies. You've got massive nasal congestion even when it sounds like you are not infected with anything such as a major cold. You've got inflammation in the respiratory tract as well, with asthma and itchy throat, and you frequently get sinus infections from all the junk being trapped up in there (through congestion/inflammation).
It seems to me that you've endured an awful lot - years of shots, years of using an inhaler and meds, lots of runny noses, nasal washes. So what you're doing isn't working.
Soy is nature's protein, and people have eaten it for 5000 years without problems. Only in the last 30 years or so have we had this huge uptick in reactions to it, as well as to eggs, dairy, tree nuts, legumes, eggs and a zillion other foods. Only now do we have this huge increase in asthma.
So, while it's possible you are reacting to one element, it's also likely that you are reacting to so many of these chemicals you have (understandably) been introducing to your body to control your symptoms.
I had a lot of allergies too (cats, pollen, ragweed, dust, mold) and I have a lot of friends who've had much worse, including foods. One friend of mine has a son who had 60 food triggers - the child basically could not eat. Another friend walked around with a box of tissues under her arm - allergic to 68 of the 72 items on the allergy scratch test. She also got shots and took prescription and over-the-counter meds at the same time. Her son spent the first year of his life on a nebulizer 3 weeks out of 4. I had a lot of sinus infections and bronchitis too. We're all healthy now.
The problem is our diets - our foods are processed, and our natural foods are nutrient deficient. Panels of doctors and nutritionists and food scientists have determined that there's no way to even get our basic vitamins and minerals without consuming some 5000 calories a day - which of course is not possible.
The key is to supplement intelligently with a balanced, bioactive, usable formula designed to get all the nutrients in your body (and that means into the cells themselves) at the same time, where they work together. Swallowing handfuls of pills (whether vitamins or medications or whatever) just gives the body more work to do, and only 15-30% are absorbed anyway (along with all the fillers and junk used to make the pills hold their form).
As you've observed, it's almost impossible to completely screen out offending ingredients. You just can't spend your life reading labels. The point is, you should not be reacting to soy, whether it's tofu or soy lecithin or anything else. You should be able to eat anything you want.
So what you need is something to help strengthen your immune system and give your cells the fuel they need to perform properly, rather than going haywire. All of the advances in epigenetics are proving this - in dozens of scientific papers, clinical trials, and lots of exposure in news magazines or programs like Dr. Oz. I think you'd be astounded at what you can accomplish in 2-3 months of good cellular nutrition. I've attended a lot of seminars and webinars, like my colleagues, and we've listened to the scientists and the doctors and the educators who are changing the way we look at illness and health care in this country. You should consider this - it will change your life. Let me know what you think.