The best way to determine your allergy is to keep a food journal.  Try cutting out one different food a day, start with dairy and see what happens.  My friend's son is allergic to oats, eggs, and whey.  Those are pretty uncommon foods to be allergic to so you may be eating something that you don't even realize you are allergic to.  You would generally have a reaction a short time after eating the offensive food so try and mark the timing of what you have been eating.  In my personal experience, I am not allergic to food but have similar reaction when exposed to types of dogs, horses, and very dusty spaces.  Hope this helps!  Good luck!