One of my terriers was prone to a similar condition and we went down the same route with the Vet, he reckoned it was a pollen allergy. I was told by a friend to try sulphur tablets. I got the little homeopathic pillules in a dispenser from a health food shop, and gave him the child dose to start with. After a few days the redness went away, then his itching lessened, after a week or two new hair growth! I went back to the Vet and told him what I'd given him, he said old fashioned method - sulphur cools the blood, it works, so do it. Each Spring I started him on the tablets before the itching started and it did the trick. Doesn't work with all dogs though, my other terrier itches in Summer, sulphur reduces the redness & heat in his skin but doesn't stop him itching. It's definately worth a try and much cheaper than Vets fees. Hope it helps him, good luck.