Well here's where I'm at. He's got a skin infection and ear infection, which I guess are brought on by the initial allergy.
They did a skin test, definitely no mites.
I went ahead and bought some of the special hypoallergenic dog food and will feed him exclusively that for the next 6 weeks or so to see if it's food allergies. I got him the special medicated shampoo and he'll be getting the daily bath for the next week and then every other day for a bit. And then he'll stay on the benadryl protocol.
I also got some Atopica in case the food change doesn't work. I live really far from the vet, and also will be out of town for the next month, so I'm trying to prepare since I can't easily get back to the vet.
The poor person who's going to be taking care of my dog while I'm gone. He's going to have to do ear drops every day for 14 days, the daily baths for a week ... I loathe asking people for help so this is sending me into paroxysms of guilt and stress.
I'm also washing all his bedding and toys today, although that's something I already do fairly frequently. I use a dye free, scent free detergent so I'm pretty sure that one at least isn't a cause.
Thank you all for sharing your experiences with this. It definitely helped me figure out what questions to ask and so on so I do feel like I got good service today. My vet bill today was only $270 so that too was a relief. I had been expecting so much more!
They also said that they had a dog dermatologist who visits once or twice a month so if what we're trying now doesn't work, then we can meet with him and do the testing to see if we can isolate the allergen.