I've been downing 2 32oz containers of Egg Whites a week (only 500 calories for the entire container), they're only ingredient is protein, and they're pasteurized meaning you can drink them raw (or put into a smoothie raw). I don't use the powdered stuff, but they're usually made in the same plants.
I've heard on the allergen front that if you only consume egg whites for a long time, you're body begins to have trouble breaking down the protein without the other proteins that would normally be found in the yolk.
So I just make sure to consume regular eggs 3-4 times a week. Worst case scenario is that you could stop consuming eggs for a few weeks and the "food intolerance" (not really an allergy) can be cleared up.