A Dog Owner's Guide to Ear Infections In Dogs

Most dogs will suffer from an ear infection at least once in their life, while some are plagued by regular flare ups. You could liken ear infections to the “perfect storm”, where several factors align to create the problem; for some dogs those factors are long term (for example an allergy or a weak immune system) and infection keeps recurring. Key to successful treatment of both short and long term ear issues is identifying all the triggers and correcting them individually.

Real World Example: A Shih Tzu with Sore Ears

An example of this is a patient of mine, a petite Shih Tzu called Megan. Overnight her apparently healthy ears had a habit of flaring into an inflamed, discharging mess. This happened so frequently that her owners, desperate to ease their pet’s distress, brought Megan to see me.

Their previous vet had suggested the answer was surgery, but Megan’s owners were reluctant. So instead, after discussion we decided to dig a bit deeper and investigate all possible causes of Megan’s problem.

Ear infections are a symptom rather than a diagnosis. Typical trigger factors include parasites, allergies, water in the ear canal, poor anatomy, yeast infections, and growths  Happily, Megan’s investigation yielded an answer, and we solved her problem…but more of this later.

Sounding the Alarm – Does your dog have an ear infection?

Here are the signs to be alert for:

  • An excessive amount of wax
  • A discharge from the ear (pus or blood)
  • A bad smell originating from the ear
  • Scratching or rubbing the ear
  • A head tilt to one side
  • Discomfort when the ear is touched
  • Angry looking inflamed skin around the ear canal and the ear flap
  • The skin around the ear canal and flap is thickened, slightly greasy, and discoloured (If in doubt, compare one ear with the other.)

What NOT to Do if your Dog has an Ear Infection

If you see any of the above, check in with your veterinarian.

  • Do not delay: Ear infections rarely clear up of their own accord. Delaying treatment makes curing the problem harder, which means more discomfort for the dog and more expense for you.
  • Do not use old medications: If your dog is a repeat offender, don’t be tempted to use old ear drops prescribed on a previous occasion. Not only will the drops have gone “off” (the active ingredient deteriorates once opened) but the ear canal needs checking to make sure the eardrum is intact and it’s safe to use the meds.

Each time the dog has an ear infection your veterinarian needs to:

  • Check for signs of a ruptured ear drum
  • Check for foreign bodies in the external ear canal (eliminate this as a cause of infection)
  • Build up the clinical picture so as to better understand the pattern of the problem.

The Anatomy Of A Dogs Ear

To appreciate the importance of a proper veterinary examination, it helps to understand the anatomy of the ear.

The canine ear divides into three parts:

I    The external ear:         Consists of the ear flap, ear canal, and the eardrum

II   The middle ear:           A bony chamber containing the hearing apparatus

III  The internal ear:          Containing the balance apparatus.

Why does anatomy matter?

For a start, the symptoms vary depending on where the infection is. This article deals with infection in the external ear (what vets call “otitis externa” – otitis meaning ear, and externa meaning external).

Infections in the middle ear lead to deafness, whilst the inner ear causes loss of balance and signs similar to a stroke. The eardrum acts as a shield to protect the middle and inner ear. If this shield is broken, infection or drugs can affect the delicate workings of the ear. In practical terms this means an infection in the external ear or treatment used inappropriately, could enter the middle ear, leading to considerable pain and distress.

What are Typical Triggers for Ear Infections in Dogs?

I mentioned an investigation into Megan’s trigger factors. So what are these factors and why do they matter?

Bacterial infections

If your dog’s ear is smelly, and especially if there’s a purulent discharge, the chances are he has a bacterial infection.

Bacteria are normal inhabitants on canine skin and don’t cause a problem because the skin’s immune system keeps them in check. When the immunity dips, the bacteria take advantage and overrun the skin’s defences, resulting in infection. This happens because either the skin is damaged or the animal is under the weather.

Sometimes there is a simple explanation, such as the dog went swimming and got water in his ear. Water macerates the skin (this is what happens when you sit too long in the bath and your fingers go all prune-like).  This soft, swollen skin has weakened defences which leave it vulnerable to bacterial invasion.

Our example of a dog that went swimming is a useful one, because the water may be long gone by the time the infection becomes obvious. As a vet, I can clear up that particular episode, but when the dog goes swimming again there’s a good chance of it recurring.

Yeast Infections

Yeast thrives in warm, damp places, which makes the ear canal prime real-estate where they are concerned. Again, just like bacteria it is normal to have yeast on the surface of the skin but weakened immunity allows the yeast to take over.

Your veterinarian diagnoses this condition by staining a sample of discharge from the ear and examining it under the microscope for the skin yeast, Malassezia, with its typical “cottage loaf” shape.

Parasitic Infections

When it comes to ears, the parasite with that is top of the heap is the ear mite, Otodectes cyanotis, which accounts for around 10% cases of otitis externa. Ear mites live their entire life in the ear, and it takes close contact between pets for them to spread. Hence puppies acquire ear mites from their mother and it is especially common in young dogs. Also, when your pets cuddle up together, an infected dog may well pass otodectes on to his pals.

As a veterinarian, otodectes is a satisfying condition to diagnose as you can see these tiny white mites scurrying away from the bright light of the otoscope. A great way for you, the owner, to see these mites is on a smear of earwax under the microscope. I love seeing an owners’ reaction when a mite waves back from under the microscope.

Foreign Bodies

The classic interloper in a dog’s ear canal is a grass awn. In the summer months, a dog running through long grass snares seeds in their coat. These awns have a similar aerodynamic to a dart or arrow, and readily migrate. If the seed snags in the fur beneath the ear, it may then move into the ear canal. This causes intense irritation, and the dog may paw at the ear, scoot his face along the ground, or sit with his head tilted to one side. To diagnose this problem a veterinarian looks into the ear canal with an otoscope, and then removes the grass awn.


It’s perhaps bizarre, but some dogs suffering from food allergies present with recurrent ear infections. This is because the allergy triggers inflammation in the skin which causes irritation. The dog then scratches and damages the skin, which allows bacteria to invade.

Getting to the bottom of an allergy issue involves putting the dog on a strict hypoallergenic diet for two to three months. This allows potential triggers to clear the system. If the dog is problem free on a hypoallergenic diet, this makes dietary allergy as strong contender.


The commonest growths in the ear are not malignant (they do not spread to other parts of the body), but a nuisance because they narrow the ear canal. This causes air to stagnate in the ear, possibly even blocking the natural flow of wax out of the canal, all of which predisposes to infection. The vet makes a diagnosis by inspecting deep inside the ear canal with an otoscope.

What It Means When an Ear is Very Sore

It is crucial the vet gets a good look down the ear canal. However, ear infections can be so sore that it’s kinder to sedate or anesthetise the patient during this examination. This also allows an opportunity to collect samples of wax to look at under the microscope, and swab the ear for culture and sensitivity. That said, if this is the dog’s first episode it’s quite normal to treat without an investigation in the anticipation of it settling uneventfully. If however the ear infections are regular, or difficult to treat, the vet will want to investigate.

Investigating Ear Infections In Dogs

This may be a two-pronged attack. The veterinarian settles the symptoms (i.e. the sore ear) and also looks for the underlying cause.

The Ear

The otoscope is a special torch like device, fitted with a lens and different sized heads to look deep inside the ear canal. A high-tech alternative is a video endoscope, but the patient needs to be sedated for this. The later has the advantage that the video allows you, the owner, to better understand the problem.

The Bigger Picture

The vet then looks at the bigger picture to search out issues that predispose the dog to ear infection. Typical examples include underactive thyroid glands, Cushing’s disease, diabetes (these three weaken the immune system) and food allergy. [$]

These first three conditions are diagnosed on blood tests, whilst food allergy is best diagnosed via a dietary trial.

Remember little Megan?

All her tests came back normal, which left food allergy a strong suspect. After discussion, her owners were happy to put Megan on a special diet to test out this theory. The idea is, in the absence of allergens there should be no symptoms – so no sore ears whilst on the special diet points towards food sensitivity.

However, there are downsides to a dietary trial. For a start, you need strong will power not to give any treats or snacks for the 12 weeks of the trial, or this undoes all that good work. However, Megan’s owners did magnificently well, and at the end of the three month period the ears hadn’t flared up once – wholly remarkable for her.

Treatments for Ear Infections in Dogs

Mild Ear Infections

We treat mild cases of otitis medically, often with topical treatments (drops in the ear) rather than oral medications. However, an obvious problem is that the ear may be too sore for the dog to tolerate drops. For this reason, your veterinarian may first give an anti-inflammatory injection, to reduce the soreness, and then continue with drops.

Another problem is gunky discharges stop the drops getting where they’re most needed. To counter act this, the vet will either clean the ear in the clinic or sedate the dog for a thorough ear cleaning.

Most medicated ear drops contain a combination of the following:

  • An anti-inflammatory:     To take swelling down from the ear canal
  • A local anesthetic:            To reduce the pain
  • An antibiotic:                    To fight bacterial infections
  • An antifungal:                   To kill yeast infections
  • An acaricide:                    An ingredient that kills ear mites

Most drops are put in once or twice a day, for a period of 7 – 21 days depending on the response to treatment. In addition, if the vet suspect ears mites, there are several spot-on anti-parasite products that kill ear mites (the drops are applied to the back of the neck as usual, not the ear canal!)

More Severe Ear Infections

If the ear is particularly sore, of the veterinarian is worried about infection tracking from the outer to the middle ear, they may prescribe oral antibiotics and anti-inflammatories. These help bring the problem under control as a solo treatment, or in combination with topicals.

Complications From Ear Infections in Dogs

If a dog suffers from regular ear infections then the ear canal tries to protect itself. The skin of the ear canal becomes thickened and tough, in just the same way that a guitar player develops tough calluses on his fingertips. However, the ear canal is a tube of fixed diameter, so when the skin thickens the canal narrows. This can become so marked the ear canal closes over.

This creates a vicious circle because now even less air gets into the canal, making infection more likely.

And this is where surgery has a role. There are operations which can remodel the ear canal, so as to improve ventilation. Whilst this does not stop infections completely, by improving air circulation and access to the canal, it makes them less frequent and easier to treat.

Underlying Causes of Ear Infections in Dogs

Of course, of major importance is correcting those underlying causes. It is likely that a dog with underactive thyroid glands, once put on a thyroid supplement, mounts a better fight back against bacteria, which means fewer infections.

And Megan?

Well, Megan has a food allergy. But she also has a doting Nana who can’t resist giving her treats. This meant every time Nanasuccumbed to those big brown eyes and gave Megan a tasty treat, the dog’s ears flared the next day.

In an ideal world, we would control Megan’s symptoms with diet alone, but the owner knew how important it was for Nana to give Megan the odd treat. To get round this we started Megan on a low dose of an immunosuppressive drug called cyclosporine. This drug dampened down her allergic response to the certain foods.  With most of her food as a hypoallergenic diet and with a small amount of cyclosporine in her system, Megan is now free from earache, and there was no need for surgery… much to her owner’s relief.


  • Small Animal Clinical Otology: Resection of the lateral wall of the auditory canal. Rose. Vet Med Small Anim Clini 73 (1)
  • A Practitioner’s Approach to Complete Ear Care. Wilson. Dermatology Reports 4 (1)
  • Otitis Externa. Griffin. Comp Cont Ed Pract. Vet 3