I am not a medical professional and my advice isn't worth the time taken reading it...
As a child I had a horrible allergy to all grass plants (corn, lawn grasses, crabgrass, etc). I'd break out in hives, my throat would swell shut, I had to take tons of antihistamines and wear a pollen mask from March through October. One option was to move to the desert, away from all grasses. So my parents moved to the country, to a farm, with fallow hayfields full of grass and weeds, and next to a horse farm that had thousands of bales of hay brought in on a regular basis. I was stuck inside the house, miserable...but my love for horses took me next door, where I went to work, eventually unloading hay trucks. After weeks of heavy, continuous exposure, my grass allergy gradually declined. I get a 15 minute contact dermatitis reaction if I walk through a cornfield now, but nothing worse.
I was also severely allergic to beestings, but when I was stung earlier this year in the eyelid I had hardly any reaction.
I had a bunch of less-than-lethal food allergies that kept me from eating strawberries, citrus, nuts, tomatoes...all gone.
I can only say that whatever happened, avoiding the things that I was allergic to did not make me less allergic, exposure did, much like the allergy shots given (I hate needles so I avoided those!).