Disorders of the Outer Ear in Cats
A variety of skin conditions affect the outside part of the ear, called the pinna. Most conditions cause tissue changes elsewhere as well. Rarely, a disease affects the outer ear alone or affects it first. As with all skin conditions, a diagnosis is best made when combined with the results of a thorough history, a complete physical and skin examination, and carefully selected diagnostic tests.
Insects and parasites commonly cause inflammation of the pinna—resulting in redness, swelling, itching or blistering—either through direct damage from the bite of the parasite or as a result of hypersensitivity.
Allergies to environmental allergens (for example, house dust, house dust mites, pollen from trees, grasses and weeds, and molds) and foods commonly cause inflammation of the skin (dermatitis) in cats. Allergies can cause redness and itchiness of the ears. Ear infections are also common. Other areas of the body (such as the face, armpits, groin, and feet) may also be affected. Diagnosis is based on your cat's history, signs, and the elimination of other skin diseases that cause itchiness. Your veterinarian will recommend a treatment plan that may include food changes and medications. Testing can also be performed to identify which environmental allergens cause your cat's allergies. The results of this test allow your veterinarian to prescribe "allergy shots" (called allergen-specific immunotherapy) to potentially help reduce your cat's allergic reaction. Allergies are a longterm condition that usually requires life-long management.
Auricular chondritis is inflammation of the cartilage within the external ear. It is rarely diagnosed in cats. Signs include pain, swelling, redness, and deformed pinnae. Both ears are usually affected. Some cats will also have signs in other parts of the body, including the joints, eyes, and heart. Treatment may not be necessary if the cat is not in pain and if only the ears are affected. Medications may help cats with pain or with signs in other parts of the body. With or without treatment, the ears will be permanently deformed.
In some cats, the inner, hairless side of the ear can become inflamed and irritated after the application of certain ointments or medications. This inflammation, called contact dermatitis, can develop 1 to 7 days after starting a treatment. The skin of the ear can become red and swollen and have bumps or sores. Some cats will also be itchy or in pain. Veterinarians typically treat the condition by stopping all ointments or other topical medications. Switching to a new ointment is unlikely to help, because most products contain similar inactive ingredients.
Ear hematomas are fluid-filled swellings that develop on the inner surface of the pinna (outer ear). The cause for their development is unknown. Signs include head shaking or ear scratching due to itchiness. Treatment usually involves surgery to drain and flush the swellings. Frequently, the veterinarian will place a drain made out of a soft tube in the area to help prevent fluid from building up again. Medications may also be prescribed.
Frostbite may occur in cats poorly adapted to cold climates and is more likely in wet or windy conditions. It typically affects body regions that are poorly insulated, including the tips of the ears, feet, and tail. The skin may be pale or red, swollen, and painful. In severe cases, tissue death and shedding of the tips of the outer ears may follow. Treatment consists of rapid, gentle warming and supportive care. Amputation of affected regions may be required but should be delayed until the true edge of the affected tissue is determined.
Several disorders in cats can result in hair loss (alopecia) on the ears. Periodic pinnal alopecia causes patchy or complete hair loss on both pinna (ear flaps) of Siamese cats. Treatment is not necessary. Pattern baldness can affect only the pinna of young dogs and cats. Medications used to treat baldness in dogs and people should not be used on cats, because it has caused the death of at least two cats.
Several immune-mediated diseases may affect the outer ear and the ear canal (also see pemphigus). Other areas of the body are typically affected at the same time and may include footpads, mucous membranes, skin and mucous membrane junctions, nails and nail beds, and the tip of the tail. Immune-mediated diseases are confirmed using a biopsy of primary lesions.
Cats can develop inflammation of skin (dermatitis) after being bit by insects that feed on blood, such as mosquitoes, fleas, and flies. Small bumps typically form on the tips of the ears and may be covered with scabs or develop into sores.
An allergic reaction to mosquito bites can cause an inflammation of the skin with crusted, slow-healing sores on the outer ears, nose, and rarely the footpads and eyelids of cats. Often referred to as miliary dermatitis, these tiny “millet seed” eruptions will crust over, ooze, then dry, leaving a small patch of hair loss. In severely affected cats, the affected areas progress from small, hard round bumps to raised, white to pink tumors to crusted, slow-healing sores that merge together to affect extensive areas. The amount of itching varies and lymph nodes may enlarge. Treatment includes keeping the cat inside and using a prescribed insect repellent when exposure to mosquitoes is anticipated. Be sure to use only repellents prescribed by your veterinarian and specifically made for cats.
The rabbit flea is found mainly in Europe and Australia and can be transmitted to cats. The fleas adhere tightly to the skin of the cat and typically affect the tip of the ear, where it may cause inflammation to the skin.
Biting flies (for example, stable flies and black flies) can also cause dermatitis after biting cats. Treatment includes controlling the flies in the environment (for example, by cleaning up animal waste) and using anti-inflammatory medications prescribed by your veterinarian.
Mange is caused by microscopic mites. There are several types of mites that cause mange. One of the most common types of inflammation of the external ear canal (otitis externa) in cats is otodectic mange, caused by Otodectes cynotis mites. The mites affect the skin as well as the ears, and signs include redness, partial loss of hair, itching, and general inflammation of the skin.
Sarcoptic mange, caused by the parasitic mite Sarcoptes scabiei is rare in cats. The condition begins with small, hard round bumps on the skin. These bumps progress to scaling, crusting, and raw, irritated areas on the ear edges and other parts of the body. Itching is severe. Transmission is by direct contact with infected animals or contaminated objects.
Notoedric mange, caused by Notoedres cati, is more common than sarcoptic mange in cats. It causes intense, constant itching around the ears, head, and neck. Signs include head-shaking, redness, hair loss, and crusted, grayish-yellow scabs.
The diagnosis of mange is based on signs, history of exposure, examination, and discovery of mites on multiple skin scrapings. The mites are difficult to find, so your veterinarian may recommend treatment even if an infestation is not confirmed. Treatment options include dips and medications effective against mites (applied to the skin or given by mouth or by injection). Corticosteroids may be given to help control severe itching. Your veterinarian will be able to prescribe the best treatment for your pet. Because mites can survive off the host for a variable amount of time, all bedding, brushes, and objects in your cat’s environment should be thoroughly cleaned. Any other cats or dogs in the household should be considered infested and should also be treated.
Proliferative and necrotizing otitis externa is a rare disease in cats, and the cause is unknown. It can affect cats from 2 mo to 12 yr of age, with most cases occurring at 4 yr of age. No breed predilection has been reported, but it may be more common in males. It most commonly affects the inner surface of the ear and the area near the ear canal, but it can also extend into the ear canal. Other skin surrounding the ears, eyes, and mouth may also be affected. Affected areas may have thick crusts that may bleed or ulcerate. Secondary bacterial and yeast infections may worsen the condition. Most cats appear do not pay much attention to the affected areas, but mild itching and discomfort may follow when ulceration develops. Diagnosis is confirmed by a skin biopsy. Some cases may clear up on their own, but only after 12 to 24 mo. Treatment with topical medication may resolve the signs.
Sebaceous adenitis is a rare skin disorder of cats that involves inflammation and destruction of the sebaceous glands (glands in the skin that produce oils). The cause is unknown but it may be inherited. Signs include hair loss and scales that stick to the hair shafts on the pinna (outer ear), forehead, face, tail, and body. Itchiness, when seen, is usually associated with a secondary skin infection. The condition is diagnosed with a tissue biopsy. Treatment includes medications and medicated shampoos. Your veterinarian may make additional recommendations to increase the effectiveness of bathing routines.
Feline solar dermatitis, also called radiation or ultraviolet dermatitis, is seen most commonly in white cats or cats with white ears that have had longterm exposure to the sun. The first signs are a reddening of the skin and scaling on the sparsely-haired tips of the ears. Crusting, discharge, and slow-healing sores may develop as the skin undergoes transformation into a form of cancer called squamous cell carcinoma. During early stages of the disease, treatment consists of limiting exposure to sunlight by keeping the cat indoors between the hours of 10 am and 4 pm and the use of sunscreens that your veterinarian will prescribe. Squamous cell carcinoma of the outer ears is treated with surgical removal followed by radiation treatment, or a topical medication.
Ticks can cause irritation at the site of attachment and may be found on the pinna or in the ear canal. The ear tick, found in the southwestern United States, South and Central Americas, southern Africa, and India, is a soft-shelled tick whose younger, immature forms infest and live on the external ear canal of cats and other animals. Signs include head shaking, head rubbing, or attempts to scratch the ear. Both the animal and the environment (including all bedding) should be treated using the compounds prescribed or recommended by your veterinarian. Secondary bacterial or yeast infections also occur commonly and need to be treated.
Vasculitis is inflammation of blood vessels and is an uncommon disorder in cats. The skin of an affected area develops purple spots, redness, sores, and scabs. Shedding of dead tissue can also occur. Vasculitis typically affects the pinnae, tail, and footpads. An inappropriate immune system response, drugs, infections, or cancer can cause the disorder; however, the cause may be unknown or difficult to identify. Treatment involves eliminating any known cause as well as medication to reduce the effects of the immune system.
Also see professional content regarding diseases of the pinna.