Of course you don't want to put anything on a cat's dry itchy patches that you don't want the cat swallowing. I get eczema myself, and used to glop Desitin ointment on the tops of my feet when they were rendered huge itch patches by dry weather. And if you take the zinc and petroleum out of Desitin, what do you mostly get? Cod liver oil. A cat can eat that, right?
Smudge had a big eczematous lesion above and beside his eye for months - the moment it would start healing (and itching) he'd start whacking at it. So one night I volunteered to "rub his itch" - after dunking my finger in cod liver oil.
Well, he washed for about 45 minutes, torn between "You got goo on me!" and "This goo sure tastes good!" And it looks less red and angry today. I don't know if I'll get away with it again, but I really think it helped.