I agree with the others, in that it might be some sort of allergic reaction.
Do you have any place you can find some sulfur soap? Bathing him in this may help with the itching. It's basically similar to what they do when they give them a lime sulfur dips, which is what Maks had done when he was a kitty and had scabies. It may give him some relief.
There are only two rules at my house: House rule #1. Cats rule. House rule #2. See rule #1.