I don't think I have ever seen a problem with milk in tuna. There is often soy in it but I have fed my dairy allergic kiddo tuna since he outgrew his fish allergy with no issues. I have used bumble bee I know and a few store brands.
Other sites confirm that hydrolyzed casein or soy are in some brands, but didn't list which ones. Also, some tuna is packed in soy oil. You'll have to read the ingredients on the cans available in your area.