Allie the Allergic Elephant
I just purchased this book for my 2.5 year old daughter. It's pretty good, and gives me a good way to start teaching about safe and not safe food. It's probably more understandable to a 3 or 4 year old, but now she is going around saying "No nuts!" when I hand her food to eat. She also knows that her Medical Id bracelet for the public places means "No Nuts!"
It breaks my heart a little bit, but I'm happy to see that there are tools to help her understand her situation.