My 3.5-year-old Chihuahua has had an ear infection for close to nine months. He has had multiple rounds of various medications prescribed by my veterinarian and the problem comes back every time. When the medications stop and the problem comes back, my dog is constantly shaking and rubbing his head on either our carpet or my hand. He has periods after medications where he has no symptoms for a few months, but then the head shaking and bright red ears start again. He has had so many medications and has good days and bad days. I know it may be allergies, but the tests are very expensive and he still may not get better. He's eating the same things he ate for the first three years of his life. He has slight hypothyroidism, yet not enough to need thyroid replacement. Can you please give us some more ideas? My dog has been so miserable for so long. Thank you!
From the description of your dog's history and clinical signs, it sounds as if you're having to continually treat the result of a problem, rather than the underlying problem itself. Recurrent yeast or bacterial skin infections are typically not going to occur on their own, rather they are almost always secondary to another underlying problem. Unless you eliminate that underlying problem, you will be continually dealing with these flare ups. The medication prescribed may simply be helping because it contains a steroid anti-inflammatory; however, it is not treating the underlying problem.
You are correct that sensitivities (i.e., environmental and food allergies [even if he has been on the same food his entire life]) could be triggers for chronic ear inflammation. Underlying structural abnormalities, such as polyps, tumors or narrowed ear canals can also lead to chronic secondary infections. At this time, I recommend you pursue consultation with a board-certified veterinary dermatologist. A dermatologist will have the most focused and comprehensive approach to diagnosing and treating the cause of these recurrent problems. While you are correct that some initial diagnostics to determine a cause can be costlier, you will not only save money on long-term management, you'll also have a much healthier and more comfortable dog!