My basenji/whippet mix scratches alot too. I give her a children's benadryl (hidden in peanut butter) daily. It seems to help. She had an allergic reaction to something the Thursday before Christmas. We went to the vet on that Friday and got a steroid shot and pills. It rash cleared up overnight and hasn't returned. We still don't know what she is allergic too. The vet did suggest the benadryl and I would rather do that daily and hopefully not have to give her anymore steroids.
Food allergy perhaps? We had that problem with one and it was anything with wheat flour in it. Little skin rashes or hot spots.
I guess it could be any number of things.