Ear infections hurt. Anyone who has ever suffered from an earache knows it is right up there with a toothache and giving birth! This is bad news since ear infections in dogs are surprisingly common, affecting up to 20% of dogs. This article will help you understand otitis externa in dogs; the causes, treatments, and tests that may be necessary to get things sorted out.

What is Otitis Externa?

The clue is in the words “otitis” meaning ear inflammation, and “externa” meaning external or outside. What other sorts of an ear is there? Actually, the ear is divided into three regions:
  •         External ear: This involves the ear flap (pinna) and external ear canal. The latter is the tube connecting the pinna to the eardrum (tympanum)
  •         Middle ear: This is the bony chamber sitting downstream of the eardrum, which contains the tiny bones (ossicles) that translate the vibrations of the eardrum into what will ultimately be heard as sound
  •         Inner ear: This third and final chamber contains the balance organs.
Each part of the ear can become inflamed or infected causing different symptoms, but for now, we’ll zoom in on the most common one - otitis externa

Symptoms of Otitis Externa                                                                    

From scratching the ears to a bad smell, there are several signs that will alert you the dog has a sore ear.
  • Scratching the ear or scooting the head along the floor
  • Shaking the head frequently
  • Holding the head tilted to one side
  • A bad smell
  • A discharge from the ear canal, which may be waxy, purulent, or bloody.
  • A hot ear
  • A thickened or distended ear flap
  • A narrowed ear canal (If in doubt, compare with the other ear)
  • Change in the dog’s character, such as being withdrawn, not eating, or unusually grumpy.
If you spot any of these signs then a vet check is in place. Otitis caught early is much easier to treat than a well-established inflammation with its complications.

The Causes of Otitis Externa in Dogs

With one sore ear looking much like another, you could be forgiven for thinking an ear infection is just that and all that’s needed are ear drops or antibiotics. However, this is far from the truth and one of the reasons vets’ dislike the term ‘canker’. The latter implies a simple condition: “Take these drops and all will be well.” Whereas the truth is that there are many different causes or sources for this condition. For example, since the ear canal is lined with skin, anything that triggers a skin allergy can set off otitis externa. Also, the canal is narrow, warm, and moist, which makes it a snuggly place for bacteria, yeasts, or parasites to thrive. Then there’s the issue of grass awns getting stuck in the ear canal, and add the damage done by scratching or rubbing…and the complications pile on. To prove a point, here are some of the common causes of otitis externa in dogs.


If your dog is allergic to pollens or other allergens in the environment, then the skin lining the ear canal can also become hot and itchy resulting in infection. In addition, food allergies have a bizarre link to ears, with acute otitis externa (sudden flare-ups) being a trademark characteristic. These dogs may respond initially to treatment, but relapse after it finishes because the underlying allergy is still present.

Ear Anatomy

Breeds such as Bassett hounds or spaniels, with long heavy earflaps, have poor ventilation in the ear canal. The ear becomes the equivalent of a steamy laundry room with the window shut, which weakens the skin and encourages yeast or bacteria to grow.

Foreign Bodies

If your dog has dangly ears and is always nose down following a scent, then be wary of foreign material getting into the ear canal. Those long ears can sweep along the ground, tangling up grass awns. The latter migrate through the hair into the ear canal where they cause no end of irritation and pain.



There are more causes of infection than just bacteria. That waxy warmth of the ear canal provides an ideal home for yeasts and ear mites. Think of the equivalent of athlete’s foot but in the ear, and you’ll understand how irritating a yeast infection is to a dog.

Grease Gland Problems

Some dog breeds, such as the American Cocker spaniel, have a tendency to overactive grease glands in the ear. Think of a teenager with greasy skin and breakouts, and the problem with this and infection becomes apparent.

Hormone Disorders

When you’re not feeling well, your skin tends to look dull and lackluster. This reflects the dip in your skin’s health and immunity. A similar dip happens when a dog is under the weather because of ill health. Typically it is endocrine disorders such as low thyroid levels or too much natural steroid (Cushing’s disease) that are linked with recurrent otitis externa in dogs. This is a reflection of the imbalance within the body weakening the ears’ ability to fight infection and stay healthy.

Investigating Otitis Externa

If your dog has a clean bill of health and this is his first ear infection, the vet may well treat it and see what happens. Fair enough. However, if the dog gets repeated infections then an investigation is warranted. The tests most often run include:
  •         Examining the ear with an endoscope
  •         Culturing the discharge from the ear canal to find out exactly what bacteria are present
  •         Looking at wax samples under the microscope
  •         Blood tests to investigate the dog’s underlying health
  •         Work up any potential allergic conditions
This is because treating the ear in isolation, without correcting the underlying problem, is unlikely to work in the long term.


Otitis Externa Treatment

For that first-time ear infection, the dog may well be prescribed a course of ear drops. These often contain a cocktail of medications that soothe irritation and fight bacterial and yeast infections. For those dogs who dislike having their ears handled, (especially when sore), vets now have a slow-release medicated gel that is placed in the ear so you don’t have to do anything at home. A second treatment seven days after the first is all it requires and the results are impressive. But for the dog with sore ears who attend the vet so regularly his owner has a favorite seat in the waiting room, then a thorough investigation should point to any underlying problems which need addressing for the ears to settle down. Examples include:
  • Anti-inflammatory medications
  • Hypoallergenic diets for allergic dogs
  • Thyroid supplements for those with underactive thyroid glands
  • Parasite treatments
  • Regular cleaning to remove excess grease
From acute otitis externa that flares overnight, to long-term conditions, be vigilant and check your dog’s ears regularly. Unfortunately, otitis externa in dogs is unlikely to go away by itself and may well develop complications, so do your pet pal a favor; spot it early and seek help right away.