Ear Infections in Dogs and Cats

By Nancy Otten, Animal Health Technologist

How do you know if your pet has an ear infection?

There are three different types of ear infections: otitis externa (inflammation of the outer ear,) otitis media (inflammation of the middle ear,) and otitis interna (inflammation of the inner ear).  In order to understand the symptoms your pet is exhibiting, it is necessary to know a bit about the anatomy of the ear.  The outer ear consists of everything from the ear drum to the outside.  It is responsible for gathering sound waves and directing them to the ear drum which vibrates accordingly.  The middle ear is found on the other side of the ear drum and contains the ossicles which are three little bones that gear down these vibrations and transmit them to the inner ear.  The inner ear is where the geared down vibrations from the ossicles are translated to nervous impulses by nerves within the cochlea. These impulses are then transmitted to the brain and the sound is heard.  The inner ear is also where we find the semicircular canals that help with the maintenance of balance.  The middle ear is connected to the nasal cavity and is involved in equalizing the pressure on either side of the ear drum.   

Most ear infections are of the outer ear variety.  The animal may have some or all of the following symptoms: a terrible odour from the ear, scratching or rubbing of the ears or head, discharge from the ears, redness or swelling of the ear canal, shaking of the head (which can lead to aural hematomas,) and painful ears.  Infections of the middle ear will solicit these same symptoms but may also result in facial paralysis.  Because the facial nerve runs along the middle ear, otitis media may lead to inflammation of this nerve causing difficulty in swallowing and droopy eyelids.  An animal with an inner ear infection will exhibit the same symptoms as an outer ear infection plus may experience a loss of balance, a head tilt, and a tendency to circle.  This is because the inflammation affects the semicircular canals involved in balance. 

What causes ear infections in our pets?

The ear mite is a common culprit in kittens, but less common in puppies, and rare in adults (adults can become infected if an infected puppy or kitten is introduced into the household.)  Ear mites cause severe inflammation and itchiness.  As if this isn’t bad enough, it may lead the animal to scratch so much that it causes trauma leaving the ear susceptible to secondary bacterial or fungal (yeast) infections.  This phenomenon is also seen when an animal gets a foreign body in its ear (usually plant material.) The object itself may inflict trauma, or the itchiness and discomfort caused by the object may lead the animal to inflict trauma through scratching.  Either way, the ear is susceptible to infection.  Similarly, the itchiness caused by allergies, immune disorders, tumours, and hormonal imbalances may also lead to ear infections through self-trauma. 

A unique problem to certain breeds of dogs is that the environment in their ears is very moist and warm due to the ear’s anatomy.  Wild canids (wolves, foxes, coyotes, etc.) have upright, open ears.  This allows air to flow through the ear to keep it cool and dry.  Humans, in their infinite wisdom, have developed breeds of dog with large, pendulous ears like Basset Hounds and Cocker Spaniels.  These types of ears prevent normal air flow thus producing a warm, dark, and moist environment.  This environment is perfect for the growth of bacteria and yeast. Certain breeds of dog such as Schnauzers and Miniature Poodles have excessive hair growth within the ear canals.  Again, this prevents proper air flow and predisposes them to ear infections.  These dogs can be perfectly healthy but because of their ear anatomy will get ear infections due to ear anatomy.

Most ear infections begin as an outer ear infection.  When left untreated, the infection can progress to a middle ear and then an inner ear infection.  Rarely, due to the connection the middle ear has to the nasal cavity, a middle ear infection may occur via this route. 

How is the cause of the problem diagnosed?

A thorough examination of the ear with an otoscope (an instrument used to examine the inside of the ear) is necessary to determine the cause of the infection.  The veterinarian will look for any foreign objects or tumours, trauma, the degree of inflammation, and whether or not the ear drum is intact.  To determine what organism the ear is infected with, the veterinarian will need to obtain a swab of the material within the ear.  This is then smeared on a slide and examined for the presence of ear mites, bacteria or yeast.  A thorough history will need to be obtained and a physical examination performed to determine if there is an underlying problem or merely a simple infection.  Diagnostic tests may be needed to determine the root of the trouble.

How are ear infections treated?

Because there are a variety of causes, there are a variety of treatments.  If an underlying health problem is causing the itchiness and inflammation, this will need to be addressed.  Superficially treating the infection will temporarily solve the problem but reoccurrence is guaranteed. 

Treatment of an ear infection will almost always involve instilling some sort of liquid medication into the ear.  The ear canal is L-shaped so to ensure that the medication gets all the way in, the ear must be pulled upwards slightly when instilling the medication.  This will allow it to flow down into the horizontal part and all the way to the ear drum.  Wait a few seconds after putting in the drops to allow it to fully flow down.  Then you need to massage the ear at the base to make sure the medication is effectively distributed.  You’ll know that the medication made it to the horizontal canal when a squishy noise can be heard when massaging.  Massage it for a few seconds to allow the medication to dissolve any buildup.  Then allow your pet to shake its head.  Use a cotton ball to wipe out any debris in the outermost part of the ear canal.  Do not use a cotton swab as you may cause more damage by pushing debris back in or by damaging the ear drum.

How can we prevent ear infections?

The best way to prevent ear infections is to examine your pet’s ears weekly.  This will be especially important if your pet is predisposed to ear infections due to their ear’s anatomy or due to other medical problems.  Catching ear infections early before they turn into middle or inner ear infections is the obvious advantage.  Also, ear infections are very irritating and painful.  Diligently caring for your pet’s ears will save your friend from much pain and discomfort.  Consistently cleaning your pet’s ears with a veterinarian-approved ear cleaning solution is also a very good idea.  Not only will you nip problems in the bud but your pet will become accustomed to having its ears handled allowing easier treatment if a problem occurs.