The name I couldn't remember earlier is Neem Oil. There are lots of variations on the market, ready prepared, or you can buy and mix yourself:
The problem with steroids for allergy, is that if it is a yeast infection the steroids can make it worse. I'd definitely ask your vet if yeast infection has been considered, whilst at the same time trying a grain free diet, soothing baths (Malaseb, Hibiscrub, Nizoral) and Piriton or Atopica.
I really hope you get it sorted. My little old JRT girl had a terrible response to grass and we went through the gauntlet finding things that worked for her. I lost her last month to pneumonia after 2 wonderful years with her, but diet and Atopica definitely worked for her, not 100% but it gave her a better quality of life XX