Merck Manual

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Pet Owner Version

Otitis Externa in Cats


Karen A. Moriello

, DVM, DACVD, Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison

Reviewed/Revised Jul 2018 | Modified Oct 2022
Topic Resources

Thetubular portion of the outer ear that carries sound to the eardrum is called the ear canal. The most common disorder of the ear canal in cats is called otitis externa. This condition occurs when the layer of cells that line the external ear canal becomes inflamed. The inflammation may also extend to the ear flap (pinna). Signs include head shaking, odor, redness of the skin, swelling, scratching of the ears, increased discharge, and scaly skin. The ear canal may be painful or itchy depending on the cause or duration of the condition. One or both ears can be affected, and signs can occur suddenly or last a long time.

Inside a cat's ear

Inside a cat's ear

Otitis externa can be caused by many different factors. Some of these factors (such as parasites, foreign objects, and allergies) appear to directly cause the inflammation, while others (such as certain bacteria, yeasts, or a middle ear infection) worsen and perpetuate the condition. Identifying these factors is key to successful control of the inflammation. Unless all the causes are identified and treated, the condition may return.


A detailed history and thorough physical and skin examination can provide clues about the cause of otitis externa. The pinnae and regions near the ear may show evidence of self-trauma (from scratching, for example), redness of skin, and skin abnormalities. Deformities of the ears, an abnormal growth of tissue in the ear canal, and head-shaking suggest longterm ear discomfort.

Your cat may require sedation or anesthesia to allow a thorough examination using an otoscope. This is especially true if the ear is painful, if the canal is obstructed with discharge or widespread inflammatory tissue, or if your cat is uncooperative. An examination using an otoscope will allow identification of foreign objects or polyps deep in the ear, impacted debris, infections with parasites, and ruptured or abnormal eardrums. Often, veterinarians will take samples from the ear using a cotton-tipped applicator. Microscopic examination of the samples can quickly determine whether an infection or parasites (for example, ear mites) are present. Additional samples may also be taken for a laboratory culture (to specifically identify any bacteria or yeast causing an infection). Your veterinarian may also examine hair samples under the microscope to look for ringworm (a contagious fungal infection).

Additional tests are sometimes needed to identify the factors causing the inflammation. Allergy testing may be recommended. Cats with long-term, obstructive inflammation in only one ear may need a biopsy to look for the presence of a tumor. X-rays, computed tomography (CT scan), or magnetic resonance imaging (MRI) may also be needed if your veterinarian suspects that the inner or middle ear is also affected.


To treat these conditions, your veterinarian will need to identify and correct any underlying causes. Any pain should also be managed. Most topical ear medications contain a combination of antibiotics, antifungal drugs, and glucocorticoids (steroids that reduce inflammation). When properly applied, the ideal medication will coat the layer of cells lining the external ear canal as a thin film. Medication given by mouth or injection will probably be included as part of the treatment in most cases of longterm inflammation of the ear canal and in any case in which inflammation of the middle ear is suspected. Cats with ear mites are typically treated with antiparasitic drugs.

Because topical medications can be inactivated by discharge from the ears or excessive earwax, your veterinarian may clean the ears gently and then dry them before treatment is started. In animals with painful ears, proper cleaning requires general anesthesia. Follow your veterinarian's advice on cleaning ears at home. Many will recommend that you wait to start home ear cleanings until after a recheck appointment, usually in 5 to 7 days. Home remedies (such as hydrogen peroxide) and vinegar dilutions should be avoided. They cause swelling of the lining of the ear canal and an increase in glandular secretions, which predispose to bacterial or yeast infections. Substances that are usually not irritating in normal ear canals may cause irritation in an ear that is already inflamed. Talk to your veterinarian before putting anything into your cat's ear, and use ear products only as recommended by your veterinarian.

The treatment should continue until the infection is completely gone. Regular rechecks with your veterinarian can help ensure that treatment is not stopped too soon.

Preventive Care

Be sure to inspect your cat's ears regularly and note any unusual temperature changes, changes in skin color or condition, sudden increases in moisture or discharge, scabs, hair loss, or other changes. When you notice changes in your pet’s ears, it is time for a prompt checkup. Unless instructed differently by a veterinarian, healthy cats do not generally require routine ear cleanings.

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