Is my cat allergic to his food?

Question
My cats name is Jesse...And Jesse and I need your help! My cats ( I have 2 others) recently just got rid of fleas.(Less than 6 months ago)  We still find one here and there, but not often at all. They're basically gone. About a month ago, Jesse started to develop sores around his neck. He scratched at them until they bleed, so we took him to the vet. He told us he has ear mites, so we treated the mites, but he still scratches and the sores are getting worse. They are on his belly, back and under his chin. we took him back and they told us it could be a food allergie. we switched to pure purina cat food. his sores are getting worse, but they aren't getting better either. could he just be allergic to the food?  we've feed him the same food I'm pretty sure since he was a kitten. hes about a yr old now....his sister cambria also has a couple of sores on her neck. they all had mites, or still might have them. we treat them with ear medication every other day. what do you think the problem is?

Answer
Hi Kendra,

I have a kitty with EGC (Eosinophilic Granuloma Complex) and this sounds similar, but I am thinking your kitties might be suffering from fleabite dermatitis.

Could you answer a few questions for me, please?

Did the vet do any lab tests? If so, did he specifically test eosinophils? Were they elevated if they were tested (what was the value and also reference ranges)?

Besides the ear mite medication, did the vet prescribe anything else (please give complete name of any medications, if you would <thanks!>)?

As soon as I get your reply, I will be able to offer more help.

Hugs to you and the babies,

Jules