I was on the maiden voyage of MSC Bellissima; I'm coeliac, and my son is allergic to cow's milk. I was told that gluten free food was prepared in a separate kitchen to prevent cross contamination and a different waiter brought me the gluten free menu and took my orders. I am very sensitive and I didn't have any problems at all, my son's dairy allergy was also well handled.
The gluten free options were all delicious and I didn't feel that I was missing out.
I hope this helps, enjoy your cruise, we certainly did.