My Basset Started Itching A Lot About A Year Ago,

my basset started itching a lot about a year ago, I have changed her to a no grain diet, my vet has her on Apqual, and an antihistamine, I give her weekly baths with anti-fungal/ant-itch shampoo, followed by a water/vinegar rinse, but she still itches and has fur missing in areas, as well as scratching her skin. I had her examined by an allergist, but every thing that was talked about I have done, I am at a lost