Dog Environmental Allergies itching

My 6 yr old German Shepherd is allergic to everything! Environmental and some foods which we avoid. She has itched herself raw and has done so for the past 4 yrs. we have tried everything that the dr recommended and some on our own. Nothing has worked except prednisone and it is causing urine leakage so now I have to take her off this. We cannot enjoy her just being a dog. We are retired and she is financially draining us try. We need help. The vet said we could try allergies shots but since she is allergic to so many things and you can only put so much in the serum it may not be successful. Anyone out there that can help me please I need to hear from you.
Tanya