Cat Chicken Allergy

I have a cat who has asthma and seems to also have food allergies. Whenever I give him a chicken meal he throws up immediately. This is from fancy feast. I have been feeding him other meals from fancy feast but just realized they all have chicken. So I tried to switch him to Whole Hearted since it has no chicken in its fish flavors and some turkey, but he refuses to eat it. Has anyone heard of anything like this, why does the chicken in fancy feast non chicken cans not give him a reaction and does anyone have any alternative suggestions? I don’t know what to feed him, I don’t want to feed him chicken if he’s allergic but he doesn’t seem to eat any non chicken brands.