Have you tried other meats like rabbit, lamb, venison, kangaroo, beef? You might want to read this article:
https://www.thesprucepets.com/best-hypo ... ds-4153930Thing is, food is absolutely essential to your kitty. But finding the food with the least reaction for your kitty is the key. Allergy shots, immunotherapy are all treatments but ongoing treatments. Unless the allergy clears itself, the treatments go on indefinitely and can be expensive and none too fun for your kitty.
Are you positive your kitty has an meat/fish allergy and is not reacting some supplemental food source? Pet food manufactures these days are putting in grain, vegetables, fruits that bengals do not normally eat. Actually determining the type of allergy takes time and many vets are quick to say "allergies" when that may not be the case.
I'm not a vet or tech or have any medical training whatsoever, but I would research foods that have the least amount of ingredients -- forget all the by-products and other fluff -- there are prescription diets out there as well as "sensitive" or "easily digestion" type of foods. With canned foods, you can easily research online, reading all the ingredients, and head to a local pet store and buy a can or two of what you are looking yo try it out. I believe you would rather find a food that works rather than go for medications or other treatment.
Good luck.