I've found this to be true as well. Growing up trying all sorts of options
recommended by doctors
, different medications, and during allergy season, removing myself from any sort participation in outdoor activity all helped to a degree, but nothing really "solved" the problem. Two years ago I decided to stop taking the medications and actually make an effort to expose myself to the allergens that made me miserable.
I know this is entirely anecdotal, but I haven't taken any allergy medications (even OTC) since, and this allergy season has been the mildest I've ever experienced.
I don't have the link handy, but I've also read studies where people with wheat allergies consumed wheat-based foods that made them feel sick for a number of consecutive days, but gradually the symptoms disappeared and they appeared to be "cured". It's definitely interesting.