Is this dog primarily indoors with you? And is your a/c running more to dehumidify the environment? I think you've been having a good amount of rain, right? Could this NOT be an allergy? Especially as the vet says many dogs in the area are showing these symptoms. The environment is dry, causing dry skn, and we all know that itches! Try adding a table spoon of canola oil to the dry kibble each morning. It should help the dry skin in about a week.