Here are two marvelous links that I swiped off Tim Leffel's blog. He in turn got them from some magazine.
AllergyTranslation.com and SelectWisely both provide the same service—translation cards of your allergies into bunches of languages.
This strikes me as particularly useful for people who have severe reactions to foods. I am allergic to 19 things, but I am usually able to avoid them. One is seafood, which is hard to consume by accident and easy to identify on a plate, but if I eat it, it doesn't stay down long anyway.
Another is tofu, which gives me hives. The other things I'm allergic to have less dramatic results. Unless I eat a lot of dairy. Then I'm pretty much ready to be lifted by med-evac helicopter to the nearest gastroenterologist, who will then declare me ridiculously sick, until I'm not, at which point he'll be baffled. Best avoided, and not hard to say no to ice cream once you've been in that kind of pain.