head shaking continued

Hey guys
about a week and a half ago, I posted a thread about my boy chester. He's been shaking his head for a bit, and 2 vets now have thought it was an ear infection. The current one (who I trust) wants to do an ear swab and send it over for testing so they know what kind of antibiotic to give him....and said that the old antibiotics just suppressed the infection but didn't make it go away. I'm skeptical though, for these reasons:
1. His shaking has gotten no better, no worse with either set of eardrops OR the oral antibiotics.
2. At no point has his shaking gotten worse, it seems to stay consistent.
3. Dynah has been shaking her head too...but she's so squirmy (kitten) that I can't see in them.
4. Mites have been ruled out twice (by vets).

I have taken away the newish kibble (dental formula) and they've been without it for about 10 days now. I haven't noticed an improvement in either cats, but I'm wondering if it might take awhile to take effect.

Does anyone have anything I can look at or consider? Seems odd for both cats to be shaking heads without mites, and for the one (he's a bit worse) to have irritation but no reactions to antibiotics.

What about a yeast infection? There is a normal balance of bacteria and fungi (including yeast) on the skin and membranes. A heavy dose or extended use of antibiotics can change the balance.

I don't know if cats get increased pressure in the ears as part of an allergic reaction (think sinus infection in people), but the pressure causes kids to dig at their ears. Perhaps an antihistamine & decongestant - use under a vet direction.
Food is a very common source of allergy. You may want to talk to the vet about a signle-source diet and supplements. Dietary changes can take weeks to show improvement when you are dealing with critters who don't speak our language.

hum, yeast infection could be. The vet said that there is some inflamation, but it's at the VERY bottom of the ear canal. It hurt chester so badly to get the swab done last time, that I feel guilty doing it again because I was being cheap. (couldn't warrant the $88 immediately).
I know that the anti inflammatory did work (he was given an injection), but it was only a temporary solution.
the only problem with the yeast infection is that they were shaking before the antibiotics...so it would have had to come from another source.

very odd.