Which symptom indicates that a dog may be suffering from otitis externa?

A dog suffering from otitis externa, which is an inflammation of the external ear canal, often exhibits symptoms that reflect discomfort or irritation in that area. Head shaking is a common response as the dog tries to alleviate the sensation of itchiness or pain associated with the condition. This action can be frequent and vigorous, indicating that the dog is trying to rid itself of the irritation.

Crusty eyes, excessive yawning, and bright eyes may be related to other health issues or discomfort but are not direct indicators of otitis externa. Crusty eyes could signal a range of conditions affecting the eyes or surrounding areas, excessive yawning typically suggests behavioral stress or fatigue rather than ear pain, and bright eyes generally indicate good health and alertness. Therefore, the specific behavior of head shaking directly correlates with the discomfort a dog might experience in the ears due to otitis externa.