Otitis externa in dogs is always due to bacterial infection.

• A. True
• B. False
• C. Not sure
• D. Both true and false

Answer: (B)

Otitis externa in dogs is not always caused by bacteria. The ear canal can become inflamed from several primary factors—parasites like ear mites, foreign bodies, moisture or cerumen buildup, and inflammatory or allergic skin diseases such as atopy or food allergy. When the canal is inflamed, bacteria and yeast often take advantage of the environment and overgrow, so infections commonly involve bacteria or yeast as secondary invaders. But the initial trigger can be nonbacterial, and treating only the presumed bacterial infection without addressing the underlying cause may lead to recurrence. Diagnostics should include ear canal cytology to identify bacteria, yeast, or parasites and to look for underlying conditions, guiding a treatment plan that targets both the infection and its predisposing factors.