My husband is very allergic to pineapple, of all things. He can't eat cut fruit without knowing the cutting board was washed first. He did this once and started choking, as his air passage swelled close and he couldn't breathe. We went to a large dinner once, where the ham, which had been baked in a layer of sliced pineapple, was brought out... he had to leave pretty quickly, as his nose was tingling and his breath was getting short.
It's amazing what people are sensitive to!
Did you hear that in certain elementary schools NO children are allowed to bring peanut butter sandwiches, in case one of the other children is allergic, since 'kids share lunches'? Don't know the veracity of this, but heard it on the news several months ago.