you can take a dog im sure if you need one for a handicap. I even saw an episode of airplane(i dont buy it either lol) about a woman who needed her pet pekinese in the airplane with her because she had LUPUS. Still dont get that one!
im sure if you needed a seeing eye dog...maybe. But ummmm where would they "you know...." Poo can be picked up (kinda..but ewwww..i might walk around bare foot once in a while lol) but ummm pee? yucko.