A. For a pet with chronic ear issues I would recommend checking her thyroid levels. Hypothyroidism can be a cause of chronic ear infections.
Then I would recommend having a bacterial culture of the ear debris to ensure the appropriate antibiotic is chosen to completely rid the bacteria in there. If there is resistant bacteria, the ear will appear to get better at first but then once ear meds are stopped they will thrive again and cause a re-emergency of the ear infection. Also longer treatment may be needed, for example instead of 7-10 days, perhaps 14 days continuously.
If all else fails, I would recommend a skull radiographs to look for signs of a narrow ear canal and/or an inner ear infection which will require not only topical antibiotic ointments put into the ear, but also oral antibiotics.
Most ear infections are caused by moisture in the ears, narrow ear canals, hypothyroidism or skin allergies. Each one has to be gone through systematically.
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