I am allergic to shellfish and absolutely never assume that any food served on planes is safe for me to eat. Yes, my allergy is listed in my passenger records but I always bring along enough food to survive on for the duration of the flights.

If, it happens that something offered to me on the flight is obviously completely safe, I will eat it but those items are usually entirely pre-packaged such as crackers or a dessert.

It is much better to be safe than sorry.