I used to live with a chap who was supposedly allergic to just about every foodstuff known to man. The "test" was interesting. Apparently it consisted of the chap saying "Write down on here what you think you're allergic to", then zapping him with electricity for half an hour before saying "Yes! You're allergic to everything you wrote down earlier!", and then charging him for the privilege. My other flatmate and I had mulled over the idea of allergy buckaroo, where we'd throw various things at him, and see which of us would bring him out in a rash, or whatever it was he was supposed to do.