Ear infections in dogs and cats (Otitis externa)

Ear infections in dogs and cats (Otitis externa)
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Image credit: Joel Mills ( BY-SA 3.0)

Otitis externa is inflammation and/or infection of the outer ear canal. Many factors can cause or contribute to the development of this condition. Some of the major causative factors we see at Vet Hospital Port Shepstone are:

  • Microorganisms (bacteria, yeast)
  • Skin allergies
  • Skin parasites (ear mites, ticks, fleas, mange)
  • Foreign bodies (grass awns, dried medication, dried wax, displaced hairs)

Microorganisms and skin allergies are among the most common direct causes of external ear infections.

Because of the factors mentioned above, external ear infections are very likely to recur in future. Prompt recognition (see symptoms below) and treatment are important in the initial phases of this condition. Ongoing management (mentioned later) can also prevent long-term and future ear infections and complications.

Predisposing factors include the outer ear structure (long floppy ears like with Basset hounds, hairy ears or long narrow ear canals), moist ears and diseases that obstruct the ear canal (growths, swelling of the ear canal tissue). Dogs that swim a lot (Cocker spaniels, Labradors retrievers, etc.) and those that are bathed frequently (Poodles, Yorkshire terriers, etc.) are often presented, but any dog or cat can get this condition.

Labrador retriever youngster
Labrador retrievers are very often presented to our hospital for external ear infections.

Symptoms of external ear infections include rubbing, shaking and scratching, reddening of the skin, hair loss and swelling of the affected ear(s). In many cases, a distinctive bad odour is also evident, especially when microorganisms are involved. Sometimes the condition is so bad that dogs refuse to eat and/or sleep at night.

Dogs and sometimes cats can also present with what is called an othaematoma, where one or both of the ear pinna(e) are swollen due to the buildup of blood under the skin. This is as a result of excessive shaking of the head.

When the otitis externa is severe, infections might spread to the middle and inner ear structures, causing symptoms such as tilting of the head, walking in circles, shaking of the head, often inappetence and showing reluctance to be touched around the affected ear(s). Although rubbing, scratching and sensitivity are often the only signs, middle ear infections are very painful. Inner ear infections, where the vestibulocochlear area of the brain is involved, are mainly seen by a head tilt, balance problems, a one-sided droopy face and walking in circles.

When skin allergies are involved, other areas such as the face, feet, armpits, belly and/or the area under the tail are also itchy. This will be seen by scratching, rubbing, chewing, licking, redness and hair loss of the affected areas.

At Vet Hospital, a full treatment plan for the ear infection will be discussed during the consultation. One or more follow-up examinations will also be strongly recommended.

Diagnostic tests

Many factors may come together in the development of a pet’s ear problem. Recognition and subsequent treatment of all factors are key to successful clinical management of otitis externa. With any ear condition, it is important to consult an experienced veterinarian as soon as possible.

Because there are many causative agents and the treatment differs for all these conditions, it is always recommended to know what to treat for. Depending on many factors, your family veterinarian will very likely recommend a basic ear smear for evaluation under a microscope and an otoscopic evaluation. Other tests might include bacterial cultures and an antibiogram (to determine the best antibiotic for a specific microorganism present) and even head X-rays.

Common conditions & treatment


Microorganisms that overgrow in the ears are commonly yeast infections (Malassezia), Coccal infections, mixed bacterial infections and occasionally Pseudomonas infections. The last three conditions are all bacterial infections. A combination of these organisms can also be present.

Malassezia Otitis externa
The Malassezia microorganisms prepared from an ear smear viewed under a microscope. self (CC BY-SA 3.0)

The severity, quantity and type of microorganisms are diagnosed on an ear smear. These infections can be primary or as a result of any of the other causative agents. They are treated with specific scheduled antibiotics and proper cleaning of the ear. In mild to moderate cases, one can often treat at home, but moderate to severe cases need professional cleaning under anaesthesia. Pseudomonas infections are serious and are known to be very stubborn and difficult to treat. An aggressive, long-term treatment protocol with regular follow-up examinations is indicated in these cases.

Skin allergies

Allergic dermatitis, or a skin allergy, is the result of environmental proteins, also called allergens, (commonly flea saliva [majority of cases], grass, pollens, certain food proteins but many more exist). Skin allergies are very often diagnosed on the exclusion of similar-looking conditions and a high index of suspicion. A strategic flea control program will always be recommended as even if flea saliva is not the main cause for the allergy, it only takes one flea to make other allergies worse. Trial medication and/or diet exclusions can also be requested in atypical cases.

An allergy is a developmental condition and will need lifelong management. The more an animal is exposed to a certain allergen, the more likely the animal is to develop an allergic reaction to it. Allergies can be due to the sum total of a combination of allergens or it can be due to a single source. The best way to treat allergies is by removing the causative allergen(s), but because they are often unknown or in some cases, it is difficult to do so, immunosuppressive medication, essential fatty acids and antihistamines are used. Allergies can also show a seasonal prevalence. In addition to ear treatment, prescription corticosteroids or cyclosporines are used for the control and maintenance of severe, stubborn and/or unknown allergies.

Food allergies are diagnosed through hypoallergenic novel diet trials, where a specific prescription diet such as Eukanuba Dermatosis (potato & fish proteins), Hill’s Sensitive skin (chicken proteins) or Hill’s Z/D (hydrolysed chicken proteins) is fed for a period. The theory of a novel diet is to feed a type of protein that the animal was not, or less likely to be, exposed to during its lifetime. The principle is that animals are less likely allergic to (for example potato proteins) than beef or chicken proteins.

Complete resolution of skin allergies is very important in the management of long-term external ear infections.

Ear & skin parasites

Ear parasites include Ear mites (Otodectes cyanotis), ticks and mange (Demodex spp.). These conditions are diagnosed on ear smears, skin scrapings and/or otoscopic evaluation of the ear. Because each of these parasite groups is treated with a different anti-parasitic medication, it is once again important to consult your family veterinarian for advice.

Foreign bodies & growths

A foreign body is anything that is stuck in the ear canal that does not belong there. When a foreign body is suspected, the attending veterinarian will recommend a quick otoscopic examination. This examination might need some degree of sedation in order to minimise discomfort to your pet. Removal under sedation or general anaesthesia is the treatment of choice.

Growths include polyps and cancers that obstruct the ear canal, compromising the opening and the skin of the outer ear. Surgical removal under general anaesthesia, if possible, is the treatment of choice.


Sometimes pets with chronic (long term) otitis externa have problems beyond the eardrum (middle ear infection – otitis media and inner ear infection – otitis interna). As mentioned above, these infections are very painful and rubbing, scratching and sensitivity are often the only signs. Middle ear infections are diagnosed on otoscopic evaluation under some form of sedation.

Inner ear infections, involving the vestibulocochlear area of the brain, are mainly seen by a head tilt, balance problems, a one-sided droopy face and walking in circles. Both these conditions need aggressive treatment, can take a long time to heal and even in the best efforts can cause irreversible damage.

Another common complication is the formation of an othaematoma in the pinna of one or both ears. Excessive shaking of the head and subsequent flapping of the ears can cause the little blood vessels inside the ears to burst and bleed. This blood and blood clots then accumulates between the skin and/or the cartilage of the affected ear, causing it to swell up.

Othaematomas are treated surgically where the clots and blood are physically removed through a cut in the ear and the skin is tightly sutured together.

Prevention & management

Because ear infections and their complications are known to get worse very rapidly, early recognition and treatment are very important for prompt resolution. In clean, non-affected ears, management can aid in the prevention of this condition.

Clean, dry ears will go a long way. After a bath, swim, cut or trim, make sure your pet’s ears are dry.

When an underlying skin allergy is diagnosed, strategic flea treatment, essential fatty acids and hypoallergenic foods (as discussed earlier) will help to maintain pets in an itch-free condition. When it comes to flea treatment, we recommend NexGard or Bravecto tablets. A great essential fatty acid supplement is Mirra-cote (reinforced with Zinc).

By carefully removing the hair from your dog’s ears (for example at the doggy parlour), you will discourage the build-up of fluids in the ears.

About the author
About the author
Renier is a qualified, experienced companion animal veterinarian whose main interests are animal health and strengthening pet-owner relationships.
View all posts by Dr Renier Delport (BVSc.)

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