I took a ships tour on HAL, a VERY, VERY long time ago only to discover my boarding photo with the words SHELLFISH ALLERGY written in BRIGHT RED and posted throughout food areas along with those of other food restricted sailors. It was a good system in its day.
Flash forward many years later, when we took a Seabourn tour and all those things had long since been replaced by simple computer screens. We no longer had our pics displayed on the walls like bounty hunters were seeking us out.
Of course, then came the next shakeup when preset seating stopped being a constant- and I feared all bets would be off. But it truly did not matter.
My Epipen, Benadryl,or any other resulting food repercussions to me personally have happened aboard any Seabourn ship. I have had a few issues in ports where menu descriptions were inaccurate, and I have learned to play it safe when in doubt. BUT- Carnival as a collective does well with this and I feel safe. Even when I was trapped last summer due to a familial gathering of my nightmares on a ship for 6000! Before I could say a word, waiter appeared and said, which one at this table is our shellfish allergy? I was quite impressed!