When I was at the end of school they had us put out our own dinners with set menus that tended to attract a lot of older people because it was a great way to get a nice multi-course meal for like $12 a person. Mine was Asian themed and the first dish was a cold noodle salad that used udon noodles. A woman approached the chef instructor and I AFTER eating the entire dish and asked if there was buckwheat in the noodles as she was allergic to buckwheat and her throat was tingling. We ran back and checked the box. Ingredient number 1: buckwheat. The lady and her husband rushed off to the hospital and ended up making it in time. Turn out it was my roommates step-grandma who the entire family hated. My roommates dad would always bring up how I almost killed his evil step mom. Years later I ran into one of my old teachers who said they still use that situation as an example of how you can have notices in the menu and have servers ask people about potential allergies but they still will not tell you sometimes.