Bassett hounds and allergies

Hello everyone. I adopted my dear bassett hound dog 5 months ago and he's having persistant skin problems. We changed dog food to salmon and rice. I bath him every other week and give frequent sponge wipe downs at night. He's on zyrtec as well. Does anyone know of other things i can do for him ? Could the oatmeal/aloe tropiclean medicated dog shampoo i'm using be causing problems? he's lost a ton of hair and itching a lot. My vet says we could do cipro injections but it's expense. Please help!