Client Information Sheet
Copyright Bilton Veterinary Centre 2013. All rights Reserved
Otitis Externa (“Ear Infections”)
What is otitis externa?
Otitis externa is a term that describes either an inflammation and/or infection of the outer (external) ear canal.
A dog’s ear is quite different in anatomy to that of the human counterpart. The ear flap (called the pinna) can
either be “pricked” (eg German Shepherd), “floppy” (eg Labrador) or “pendulous” (eg Cocker Spaniel).
The tubular part of the ear carries sound from the pinna to the ear drum. This is separated into two distinct
areas, called the vertical and horizontal canal. These canals are coated in a type of specialised skin called
epithelium.
The ear drum is a very thin and fragile membrane that
separates the external ear canal from the middle ear,
which is a spherical boney cavern filled with air. This
also is coated with epithelium. Just above the middle
ear is the inner ear and it is here that sound is
processed as well as the apparatus that is responsible
for balance.
Otitis externa is used to describe ear disease affecting
 The base of the pinna
 The ear opening
 The vertical canal
 The horizontal canal
Figure 1 - A Normal Healthy Dog Ear
Otitis externa can affect any/some/all parts of the
outer ear. This usually involves the pinna and ear
opening as well as the vertical canal and the
horizontal canal too.
If the ear drum is damaged then it can progress to
otitis media which describes infection of the middle
ear, and otitis interna which describes an inner ear
infection. These diseases can occur in their own
right, but they may also be a cause/effect of otitis
externa too.
Figure 2 - A Dog Ear with otitis externa
For more information, visit: www.biltonvets.co.uk/advice.html
Page 1 of 7
Client Information Sheet
Copyright Bilton Veterinary Centre 2013. All rights Reserved
What causes otitis externa?
Many factors can cause or contribute to the development of otitis
externa.







Parasites (ear mites, ticks).
Foreign bodies (grass awns, dried medication, dried wax,
displaced hairs).
Allergic disease (canine atopic dermatitis, food allergy).
Diseases causing abnormal skin renewal time (keratinization
disorders).
Hypothyroidism
Primary bacterial/yeast infections (surprisingly rare).
Structural abnormalities such as polyps or tumours.
Figure 3 - Otodectes cynotis: “The Ear Mite”
Other factors that may contribute to your pet developing otitis externa include:




Ear structure (long floppy ears, heavily haired ears, long narrow ear canals).
Errors in treating or cleaning ears (aggressive use of cotton buds deep in the ear canal).
Environmental factors such as swimming, dusty conditions etc.
Diseases that obstruct the ear canal (growths, swelling of the ear canal tissue).
Sometimes pets with chronic otitis externa have problems beyond the ear drum (otitis media and/or interna),
and so these problems also need to be aggressively treated.
“Many factors may come together in development of your pet’s ear problem.
Recognition and subsequent treatment of all factors are the keys to successful
clinical management of the otitis externa.”
What are the symptoms of otitis externa?
The symptoms of otitis externa can manifest from mild discomfort, to severe pain. Some animals with chronic
(long-term) otitis can often have behavioral problems, particularly aggression, due to the discomfort being
experienced.
Generally, signs may include:









Shaking of the head
Pawing at ear
Unusual/unpleasant smell from the ear
Redness of the ear flap
Thickening of the skin on or around the ear
Narrowing of the ear canal opening
Obvious abnormal discharge seen on the pinna (ear flap) or down side of face
Yelping when head stroked
Increase brown/dark wax secretion visible
For more information, visit: www.biltonvets.co.uk/advice.html
Page 2 of 7
Client Information Sheet
Copyright Bilton Veterinary Centre 2013. All rights Reserved
Figure 4 - Labrador with unilateral otitis externa. The picture on the LEFT is the normal ear, compared with the RIGHT
picture which shows the affected ear
What tests are needed?
Often it will be obvious when your pet is suffering from otitis externa, but the following may be necessary to fully
understand the nature of the problem:

Examination of the ear with an auroscope to gauge the extent of the problem. This allows your vet to check
for foreign bodies, growths etc. Also allows us to see if the eardrum is intact, and the severity of the problem.
In some animals, the ear to too painful to allow a full examination straight away. If extremely painful, the
dog may require sedation or sometimes a full anaesthetic to assess the extent of the problem.

Full body examination, to check for the presence of other diseases, or predisposing factors, such as allergy or
parasites.

History taking, this lets us discover if anything has changed that may have triggered the problem, such as
changing diet, moving house, building work, swimming etc.

Cytology involves taking a small sample from the ear canal with a special cotton bud and then examining it
under a microscope. We can check for evidence of yeasts, parasites and bacteria. Also can be useful for
predicting the presence of pathological bacteria that may require further testing.

Culture and Sensitivity. This is where a deep swab is taken from the ear and then the specific bacteria are
cultures, identified and then subjected to a variety of antibiotics to find out which ones they are sensitive to
and which ones they may be resistant to.

Blood tests are occasionally warranted if underlying metabolic disease (such as hypothyroidism) is suspected
that may be contributing to the infections.

Xrays very occasionally need to be taken of the skull, if there is the suspicion of middle ear disease as well.
For more information, visit: www.biltonvets.co.uk/advice.html
Page 3 of 7
Client Information Sheet
Copyright Bilton Veterinary Centre 2013. All rights Reserved
What treatment is needed?
The choice and nature of treatment depends on the diagnosis of the underlying cause. It is important to realise
that very rarely are ear infections caused by a primary bacterial problem. In other words it is vitally important
to try and establish why the ear infection occurred in the first place. If your pet has not had ear infections before
and it is not a recurrent problem, then it is acceptable just to treat the problem as an isolated event. However it
is recurrent ear infections that are more concerning.
Ear disease tends to follow a set pattern. A normal, healthy ear is usually pretty resistant to any infection and so
in order for problems to arise – there needs to be an initial breakdown of the ears natural defenses.
This usually starts of as inflammation caused by a variety of agents – mites, foreign bodies, growths, allergies etc.
As soon as the inflammation kicks in, a chain reaction occurs involving:

The ear lining (the natural defence) being compromised

The ability for a naturally occurring yeast called Malassezia to start to get a foot-hold and build up in
numbers.

This triggers further inflammation until eventually the ear canal is so damaged that the naturally
occurring bacteria can start to get a better foot-hold too.

Eventually the environment down the ear is so abnormal, that the nastier “pathogenic” bacteria can
colonise the ear and then we have a severe otitis setting in.
This “vicious cycle” of ear disease is illustrated on the next page.
Treatment will therefore depend very much on what is causing the initial problem:
 Ear Mites – need specific treatment with anti-parasite therapy.

Foreign Bodies – need to be removed. Sometimes under general anaesthetic.

Tumours/Polyps – usually need surgery to remove them.

Poor ventilation – needs to be addressed if the ears are particularly hairy or pendulous.

Allergies – need either identifying and avoided, or controlled with medication or desensitisation.
“If there is no obvious underlying cause for recurrent ear infections, then an
allergy should always be strongly suspected.”
Animals that have an allergic otitis often show other subtle signs of allergic skin disease such as
rubbing/licking/chewing/biting at their feet, muzzle, armpits, or groin, causing hair loss and reddening and
thickening of the skin.
Very commonly food intolerances are responsible for allergic ear disease and this may be one of the first things
that we tackle when looking at possible causes. This may be the case in young animals in particular.
For more information, visit: www.biltonvets.co.uk/advice.html
Page 4 of 7
Client Information Sheet
Copyright Bilton Veterinary Centre 2013. All rights Reserved
Figure 5 - The "Vicious Cycle" of ear disease.
For more information, visit: www.biltonvets.co.uk/advice.html
Page 5 of 7
Client Information Sheet
Copyright Bilton Veterinary Centre 2013. All rights Reserved
What types of treatment are available?
Treatment normally falls into two stages
Acute treatment (rescue phase)
This aims to correct the otitis and try to return the ear to a normal healthy state. This usually involves the
application of certain topical medications and may also involve giving systemic medication as well via tablets.





Antibiotics. These are usually given topically as ear drops. However occasionally we use systemic
treatment in the form of tablets. The choice of antibiotic is important and often depends on the type of
infection or based on cytology or swab results
Anti-yeasts. These also usually given topically as they are most effective this way. They can be given
orally but side effects are more likely. Usually drugs like Ketoconazole or Miconazole are used.
Anti-inflammatories. These are vital as most otitis externa cases are extremely painful. Corticosteroids
such as dexamethasone are most useful and effective. These are often given topically but in severe cases
(or long term cases) may be given orally as well.
Ear cleaning products. When using topical therapy it is often vital to use cleaners at the same time as
these help remove unwanted debris, pus, wax etc from the ear which can reduce the effectiveness of the
topical treatments.
Ear Flush and Clean. This is sometimes required for really severe cases, and this is where we have the dog
in for a day, and under general anaesthetic actually flush and clean the whole ear canal out. This has the
advantage that we can be really thorough without hurting or upsetting the animal.
Long term treatment (maintenance phase)
This aims to try to keep the ear in a healthy state and try to reduce the chances of further flare ups. With simple
cases of otitis due to ear mites, foreign bodies etc, there is generally not much else that needs to be done. In
cases of allergic otitis however, this is by far the most important phase. Here we aim to try and control the
underlying inflammation by:


Trying to identify/eradicate the source of the allergy where possible. This is often not always possible! In
which case we have to:
Manage the inflammation by using some or all of the following:
o Antihistamine tablets
o Systemic steroid medication
o Topical steroid medication
o Regular ear cleaning
Systemic medication has the advantage of being quite easy to administer and is often
pretty potent and effective; however they often have the disadvantage of treating
the whole animal, just to see the desired effects on the ears. This can be a problem
when using medication such as steroids, which can have systemic side effects.
Therefore where possible we try and use topical treatment wherever possible, and so
a common regime that is used is:



Weekly ear cleaning
Twice weekly steroid application down the ear canals (we usually use
hydrocortisone)
Regular follow up checks to assess if current control is successful.
For more information, visit: www.biltonvets.co.uk/advice.html
Page 6 of 7
Client Information Sheet
Copyright Bilton Veterinary Centre 2013. All rights Reserved
“One of the worst things that can be done when trying to manage a
recurrent otitis externa– is to have a bottle of antibiotic ear drops
“left-over” from a previous occasion, and put some drops down
“whenever the ear seems to be a bit sore!”
This usually results in a more severe infection, and we often end
up with multi drug-resistant bacterial infection that is then
much harder to treat and resolve in the long run!”
In certain situations such as tumour/polyps or with severe chronic ear disease that has been poorly controlled
over time leading to permanent damage – a surgical solution may be advised. There are generally three types of
surgeries performed on ears.
1. Lateral Wall Resection. This is where the Vertical canal is opened up and folded back on itself. This is a
relatively simple operation but is only really useful in the case of polyps or tumours of the outer part of
the vertical canal.
2. Vertical Canal Ablation. This is where the whole vertical canal is removed, and the normal “top” opening
of the ear is closed. A new opening is created by joining the horizontal canal to the skin lower down the
face. This can only be used if the horizontal canal is normal.
3. Total Ear Canal Ablation (TECA) This is where the vertical canal, the horizontal canal and the ear drum is
removed. Often this procedure is performed with a Bulla Osteotomy (BO) as well which removes the
lining of the middle ear. This TECA-BO is probably the most useful operation, but is unfortunately the
most complex. The procedure will render the animal deaf in that ear (although by the time the surgery is
performed, most dogs will be deaf anyway due to the chronic ear disease). There are also some risks
involved with infection, swelling and facial nerve damage.
If surgery is going to be considered with your dog, one of our vets will go through the whole procedure in a lot
more detail with you. It is not a decision taken easily but often is the only way to prevent on-going and
considerable problems and suffering.
For more information, visit: www.biltonvets.co.uk/advice.html
Page 7 of 7