I really feel for you as 2 of mine have allergies and it's mostly year round here in Arizona weather. Based upon my own very difficult experience w/ allergies, I'm going to give you the best possible advice ever: get thee to a Vet Dermatologist ASAP! You can either continue going to a generalist vet who clearly knows *nothing* (based upon how he is treating these allergies!) about allergies and keep paying him time after time -or- you can make probably ONE visit to a Vet Derm and get straightened out tremendously, right from the get go. I went to my generalist again and again and wasted tons of money -- then I finally went to a Derm and got on the right plan immediately.
Stop the benadryl - it's useless in most dogs and also, it has to be given every 4-6 hrs to be effective (so, 4x a day). You could try either Zyrtec or Claritin - and both are a 1x a day dosage. BUT, I doubt those will help given the severity.
From these allergies, your kiddo's skin is then developing pyoderma (staph intermedius) which is a common skin infection in dogs w allergies. Simplicef is the very best thing to treat it, so at least your vet got THAT right, lol.
For year round allergies though, your kiddo then needs to be on either Atopica or Apoquel and/or get allergy testing and shots.
For more details on allergies, read this:
http://www.yorkietalk.com/forums/die...tart-here.html