Most cases (over 80 percent) of chronic or relapsing otitis externa have otitis media. This results from chronic inflammation of the external part of the ear canal, rupture of the tympanic membrane and establishment of infection in the middle part of the ear.

Discharge in the middle ear cavity is difficult to treat with topical therapy and often remains a source of infection. Otitis media is usually bacterial in origin.

Treatment of otitis media is based on bacterial culture and sensitivity results. Most cases require long term antibiotic therapy (minimum of two months) and aggressive topical therapy.

Most causes of otitis externa are associated with generalized dermatologic conditions. A complete dermatologic history and work-up may therefore be necessary in the diagnosis of many primary otitis externa cases. The most common causes seen in dermatology are atopy (inhalant allergies), food allergy, diseases of keratinization (e.g. primary seborrhea of cocker spaniels), and ear mites. It is critical to long term management of otitis externa that a primary cause can be found.
Related Symptoms

Clinical signs suggestive of otitis media include head shyness and pain on palpation of the ears. Some cases of otitis media might present with head tilt, circling and dry eyes, but the vast majority do not have neurological abnormalities.

As the ear drum quickly grows back after rupture, otitis media may also be present even if an intact membrane is seen on otoscopic examination. X-rays cannot be used to completely rule out the presence of otitis media since 25 percent of confirmed cases had no radiographic evidence of the disease.

In most cases of chronic otitis externa/media bacteria such as Staphylococcus and Pseudomonas are present. The color, texture and odor of the exudate from a diseased ear can provide clues regarding the underlying primary cause of the otitis and the perpetuating factors that may be involved. A dark, moist brown discharge tends to be associated with bacteria and yeast infections. Purulent creamy to yellow exudates are most often seen with bacteria such as Pseudomonas.