@ Paula M
For the best testing and treatment options consult a veterinary dermatologist.
Allergies are complicated. You need the expertise of a specialist. Intra-dermal skin testing is the only accurate way to identify environmental allergies.
In the meantime, if seeing a veterinary dermatologist is not an option right now, I would work closely with your vet, diet recommendations and all.
However, the symptoms you describe often indicate environmental allergies, food allergies are rare.
There are new treatments available now. Have you asked your vet about Apoquel? Cytopoint? Prescription shampoo? Prescription ear drops?
Often prednisone and such meds are necessary for brief periods to stop the suffering the dog is experiencing, give the dog’s system a rest and decrease the risk of infection.
Do not apply anything to her skin or use homemade remedies to treat her ears unless your vet has prescribed or approved. You could make the infection much worse.
/forums/search/environmental+allergies/ (see my posts)
