Otitis Externa (Outer Ear Infection) is an inflammation of the external ear canal that begins at the outside opening of the ear and extends inward to the ear drum.  Causes include bacteria, fungi, ear mites, accumulation of wax, thick or matted hair in the ear canal, debris, impaired drainage of the ear, and infections from elsewhere in the body.  The funnel shape of the ear canal effectively traps debris, further complicating treatment of infections.

Otitis Media (Middle Ear Infection) usually results from spread of infection from the external ear canal into the middle ear.  Foreign bodies, debris, ulceration, or improper cleaning may rupture the eardrum, allowing bacteria to reach the middle ear.  Signs of middle ear infection include odor, discharge, ear scratching, head shaking, and head tilt.  The cat may appear to be sick.