My cat’s ears have lots of crust and dirty black material

The ears in the picture have much discharge and crust, likely from ear mites, so get an ear exam and treatment at the clinic. Mite-infected cats itch and smell, with black-brown waxy discharge and crusts; untreated, they get otitis with redness, oozing, and erosion that harms hearing.

Because mites cause frequent scratching and head shaking, ear hematomas and skin infection can follow. Clean the canal with ear solution, apply anti-mite medicine, deworm externally monthly, and use an Elizabethan collar during treatment.