Sounds frustrating! A few things come to my mind. Ear mites are possible but these usually turn up on a swab. However it's possible they were just looking for infection and not parasites. Ear mites can cause hair loss on the top of the ears as well sometimes.

Another possibility is ringworm which is a fungal infection that is very contagious.

It could also be a parasite called demodex gattoi. It is not very common. Your vet would diagnose it with skin srapings.

Sounds like more tests are in order!

Dr. Marie.
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