Interesting comment on gluten consumption. In my case, it appears cumulative. (I'm not celiac, so far as I know.) I've been following a non-gluten diet for fifteen years at this point, and I can now tolerate at least a small amount of gluten without the effects I used to have.

I used to get injections to diminish my hay fever symptoms. I finally mostly grew out of hay fever around the age of forty, though I'm still allergic to horses and cats, if I have direct contact.

Don't those injections comprise increasing challenges to the immune system using the allergens themselves, to make it less prone to mount a histamine response (i.e. runny nose, itchy eyes)?