To the mom whose son is allergic to wheat, dairy, eggs, nuts and shellfish: a) that's awful and I can't imagine the stress, but b) would you actually expect all other kids not to bring foods that contain any of those things to school? 

My sister was so used to school restrictions (she has a seven-year-old) that she actually called Air Canada before a flight to ask if she was allowed to bring snacks onto the plane for her daughter (and assumed she wouldn't be able to because of allergy restrictions). Alas, in the real world, people eat peanuts.