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Advanced Veterinary Specialists

Ear Infections – What’s the Deal?

A Gray/White Cat Lying Down on Hardwood Flooring Indoors

What is an ear infection?

In dogs, ear infections are caused by yeast and bacteria that are already on the skin and in the ears. These infections do not occur spontaneously – there is typically an underlying disease that allows for them to occur. Cats also get ear infections, but they are typically caused by mites. Feline ear mites are very contagious but uncommon in indoor-only cats. Cats that go outside should receive a regular preventative that treats ear mite infestations, such as Bravecto or Revolution Plus.

Why do ear infections happen?

In dogs, ear infections are typically caused by one of three possible underlying conditions. Unilateral and spontaneous ear infections in dogs that have had exposure to foxtails or other grass awns may have a piece of plant material embedded in their ear. This can be very irritating and may lead to a secondary infection. Second, ear infections can occur secondary to moisture trapping. This may be as simple as the Labrador that likes to go swimming or the Bichon Frise that got a bath and some water in its ear, but can also occur in dogs where normal moisture is not allowed to evaporate, such as the Cocker Spaniel with large pinnas (ear flaps) that occlude its canals or the Poodle with excessive amounts of hair in its canals. The trapped moisture creates a perfect environment for bacteria and yeast that are already on its skin and in its ears to start rapidly multiplying. Finally, allergies can cause ear infections by inducing generalized skin inflammation, allowing bacteria and yeast to grow in areas that are already humid, like the ear canals and between the toes.

How to we diagnose an ear infection and its underlying trigger?

All dogs with an irritated ear require an otoscope exam of the ear canal and tympanic membrane (“ear drum”). With those that are very irritated and have had exposure to foxtails, sedation may be required to identify the plant material and remove it. A cytology is also always indicated to identify any bacteria or yeast. If an infection is identified and no foxtail is found, a dog’s breed, history, and other physical exam findings will paint a clinical picture favoring moisture trapping or allergies. If only one ear is infected, they are a larger dog, and they have a history of recent swimming or bathing moisture trapping is suspected and appropriate management can be initiated. If both ears are infected, they are a smaller dog, and they have a history of paw or skin irritation, allergies are suspected. However, some dogs are at risk of suffering from both moisture-trapping and skin allergies, such as the Cocker Spaniel.

How to we treat and prevent ear infections?

Dogs with foxtails in their ears must have the foxtail removed and any secondary infection treated. Infections are treated by cleaning the ear with an appropriate otic solution selected based on infection type and instilling a topical anti-inflammatory, antibiotic, and antifungal medication into the affected ear, also selected by infection type. Some ear medications must be administered twice daily, while others only need to be administered once. The ear cytology should be rechecked after 1 week and the dog should avoid areas with foxtails in the future. Ear infections secondary to moisture trapping and allergies are treated similarly. To prevent moisture trapping, the cause must be identified and directly addressed. Dogs that like to go swimming or are bathed regularly should have their ears cleaned with a drying solution afterward to enhance evaporation of any residual moisture. Dogs with excessive amounts of hair in their canals may benefit from having this hair plucked, although not during an active infection. Dogs with pinnas that occlude their canals are difficult to manage and may benefit from both regular cleanings with a drying solution and plucking. Finally, dogs with allergies must have their allergic triggers identified and addressed. Allergies can be broken into four categories – external parasite, contact, food, and environmental allergies. Flea allergy dermatitis (FAD) is the most common form of external parasite allergy. Dogs with FAD can have a systemic reaction to a single flea and there must be kept on an effective flea preventative, such as Nexgard, Simparica, or Bravecto. Contact allergies are caused by allergens, such as pollen or dirt, coming in contact with the skin. This typically affects the chest, abdomen, and inguinal regions, but can also cause irritation between the pads or toes. Dogs that have contact allergies benefit from having the affected areas of their body wiped down with a damp, clean cloth after spending time outside. Next, food allergies are currently very popular in media, but actually only occur in 10-15% of dogs that have any allergies. Dogs that do have food allergies typically present with intermittent to chronic irritation of the paws and/or ears. The protein source is usually the responsible allergen and these dogs benefit from a strict prescription hypoallergenic diet. Dogs must be fed only their new hypoallergenic diet for 2 months and reassessed to ensure an appropriate clinical response. Lastly, environmental allergies are caused by inhaled allergens, such as pollens, dust mites, cat dander, or a multitude of other sources, causing a systemic reaction. Environmental allergies cause a condition known as Atopic Dermatitis, which is the most difficult form of allergies to control long-term. Animals with Atopic Dermatitis present similar to those with food allergies, but may be seasonal – they may only be affected in the spring and summer. These dogs can be tested for allergen sensitivities with a boarded veterinary Dermatologist. However, identifying sensitivities does not prove that a particular allergen is responsible for a dog’s reactions. Once a list of suspect allergens has been generated based on identified sensitization and known geographical exposure, a desensitization protocol involving regular injections or oral drops will help reduce future allergic episodes in the majority of dogs. Keep in mind, this process can take several months to see benefits.

If allergy testing is not feasible for you and your dog, please speak with your primary veterinarian about Apoquel or Cytopoint, medications that can help to control skin allergy clinical signs. Apoquel is an oral tablet that reduces itch and can be given twice daily. Long-term use may increase the risk of certain cancers, such as lymphoma. Cytopoint is an injection administered every 1-2 months that similarly blunts itch but becomes less effective the longer it is used.