Otitis externa, or inflammation of the external ear canal, is a common problem of dogs and fairly common in cats. Multiple causes and factors, often involving ear infections, can cause otitis to develop.
The most common underlying source of otitis externa is allergic disease. This could be due to a food reaction, environmental allergies or even a contact reaction. These causes are often pursued when ear issues become a recurrent problem. Parasites, frequently ear mites, also can cause ear inflammation, especially in cats. Endocrine diseases such as hypothyroidism and autoimmune diseases also may need to be considered.
There are also physical factors that can increase the risk of developing otitis externa.
Certain body types or conformation that feature long, pendulous ears, such as seen in a Basset hound, can predispose to poor ventilation, as can masses (growths) in the ear canal. Hot, humid, summer weather and frequent swimming also may cause excessive moisture in the ear canal which softens the skin surfaces, allowing bacteria and yeasts to proliferate.
Unfortunately, in many cases, once inflammation starts, changes begin in the ear. The ear canal thickens and swells, further narrowing the ear canal. Treatment can become more difficult as medications instilled into the ear don’t even penetrate to the seat of the problem. Relapses are not unusual.
Young dogs are generally more prone to ear disease, as are certain breeds that either have poor conformation or are predisposed to allergic or endocrine skin conditions. Cocker spaniels, golden and Labrador retrievers and West Highland white terriers are definitely over-represented. In cats, pure bred Himalayans and Persians are more susceptible.
Signs of otitis externa include an odor, head shaking, ear scratching and sometimes pain. The affected ears may be red or swollen, and there is often ear discharge. In severe cases, the middle and inner ears may be affected. This can cause a head tilt and circling, or other neurologic abnormalities. With chronic problems that have led to scarring and thickening of the ear canals, the base of the ears can start to feel very firm — like rocks. Also, many patients with ear disease show other skin lesions.
To make a diagnosis, your veterinarian will need to look down into the ear canals using an otoscope. Many times, he or she will swab the ear canal and examine this under the microscope to identify the organisms (bacteria, yeast, or parasites) present. Sometimes an additional swab may be taken for cultures. Then your veterinarian can prescribe the most appropriate medication. Sometimes, sedation or anesthesia is necessary to perform in-depth ear flushing. In severe or recurrent infections, it can be beneficial to obtain more sensitive imaging with a CT scan, MRI or a video otoscopic exam. These procedures also require general anesthesia.
Depending on the cause, medications for otitis externa may include topical and oral antibiotics, anti-yeast drugs, anti-parasiticides and steroids. For effective treatment, it is important to not only clean and medicate the ears, but also to address the underlying reason for the ear disease. This may entail food trials to rule out a food sensitivity, allergy testing for environmental allergies so allergy injections can be started, or other laboratory work. These tests are especially important if ear infections seem to be becoming a recurrent issue. A maintenance regimen of cleaning also may be continued indefinitely to help prevent recurrent infections.
Diagnosing and treating otitis externa can require a decent amount of work, especially when looking for why the problems developed. However, by coming up with a plan with your veterinarian, you often can gain good control of your pet’s ear disease and make him or her much more comfortable.
Dr. Elizabeth Toops is a veterinary dermatologist practicing at Virginia Veterinary Specialists.