i would recommend that you find a veterinary dermatologist & make an appointment. if your dog does have a food allergy, changing food around several times can make it more difficult to diagnose & more expensive to control. your dog may also have something other than an allergy causing all of that itching. a veterinary dermatologist is experienced with all kinds of skin conditions & can often do a good preliminary diagnosis from the history of the problem & the physical exam, thus cutting down the amount of testing to determine the source of the problem.
your regular veterinarian should be able to refer you or you can locate a dermatologist through your state veterinary medical association. lisa baldwin (dickens, bark & zel) seattle, wa [EMAIL PROTECTED]