I am allergic to several common herbs and spices plus rice and peanuts. I always carry a list that has all my allergies in red and next to it a list in green of what is safe to use. When we travel abroad, I take several copies of my list in the language of the country we are visiting.
The first day on the cruise you will have to eat something simple, but after that they will give you the menu for the next day so you can order and they will use only the seasoning you can eat. You can also order lunch for the next day to eat in the MDR.
Even if you do anytime dining, they will have your order from the next day. If you go to a specialty restaurant, you should go the day before and provide them with a copy of your list.
Enjoy your cruise!