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.