We have a friend of the family who's little girl is alergic to eggs and nuts. They carry an epi pen with them. It makes it hard to cook breakfast when they come over and I have to read every package before handing out snacks/food. My wife also doesn't give me enough notice as to when they are going to stay so that I can get pancake mix that doesn't have or require eggs, etc. So she usually ends up having cereal while everyone else is eating pancakes.
I also had a customer when I worked in the resaurant that was allergic to salt. I had to wash the pans, utensils and use new ingredients for her food. She didn't come in at the busy time so it wasn't a big deal.
Thank god my kids don't have any alergies or my wife or MIL would have killed them already.
Char-griller pro deluxe w/SFB
22.5" weber kettle (rescue)