Cat Dermatitis?

There are some many things that cause this, it's hard to know.

Has your cat had a parasite exam lately (a fecal). Since it could be a reaction to those. Also make sure to use good flea control.

Head and neck lesions is usally suggestive of an allergery to a neurotransmitter and sometimes has to be removed surgically.

I would keep trying different foods to see if something else work.

Try taking your cat to a veterinary dermatologist, they can help determine the causitive agent. Your own vet can scrape one of the lesions and see if there is a bacterial infection. There are also other immunosuppresive drugs your cat can go on to reduce the reaction.

Give it time skin takes a long time to resolve

first of all use a household flea spray i recommend johnsons 4fleas in the yellow and pink can but zodiac will do as well. i would then give capstar rather than program or give johnsons 4fleas do their own version of program which is a tablet and a spot on which does work on my cats. i then recommend before putting the spot on to bathe her in tea tree shampoo made for cats it will help her skin and wash off the dirt from the fleas. add a springle of garlic powder to her food fleas don't like it and if she wears a collar some citronella dropped on to her collar should help keep them at bay.

I would take him to the vet they might have a medicaine for him.