Poor kitties...and you!

Has the vet done any scrapings for mites?
Could it be pesticides sprayed around the house or food allergies? If not pesticides, I'd look to cleaning products and maybe change the diet (bland diet of chicken, rice and lamb) for at least 6 weeks.

My gut says it's mites as I had a kitty in my past that had patches very much like those.

Maybe this could help, but please consult the vet first! http://www.petsmart.com/product/inde...ductId=2754474