After many decades of eating in restaurants, cafes, bars, and bistros, I am still waiting for a food server to approach our table with a question like this: "Does anyone at this table have any food allergies?". This may have happened to you and hopefully so. If it has ever happened to me or a member of my family, I sure can't remember it. In fact, the strongest memories I have regarding restaurant servers and food allergies goes to the other extreme. Instead of being proactive and asking prior to taking the order, several servers have either not understood "I am allergic to nuts" or not heard us when we mentioned it during the order taking. This has resulted in food sent back, food not eaten and never returning to certain restaurants. Perhaps the worst case was the server that brought the dish soaked in peanut oil and when reminded that someone had a strong allergic reaction to nuts, said "So?"
I think I need to follow the example of a pre-teen girl I observed (and later spoke to) at Denny's one morning. When the waitress arrived at her table (she was seated with four constantly talking companions), she engaged the waitress privately with a clearly printed laminated card that stated two things:
1. she had strong food allergies
2. the three food items that caused her to react.
Nothing about what the reaction was, how strong the reaction could be, what might happen if the restaurant failed to heed her warning - just a simple message.
She said it worked almost all the time and that she had found examples of such cards online. Of course I immediately forgot the name of the website just after I spoke with her. It might have been foodallergy.org which seems to have some card templates although they seem more verbose than her card.