Outer ear inflammation in the dog

by Shane Jackson M.A., Vet MB., MRCVS


This dog had suffered chronic otitis externa that had been neglected.
Consequently, by scratching the ear, the dog had severely damaged
the ear flap (pinna) thus it was necessary for it to be surgically removed
as well has having surgery on the external ear canal. She was adopted soon
after the operation and through careful management of her allergic skin condition
she lived a long and happy life. 

‘Canker’, better known as outer ear inflammation/disease or otitis externa, is a very common problem with many dogs, but the severity and frequency of occurrence will depend on many factors.  One of the main underlying reasons for otitis externa developing in an individual is the dog’s breed and its conformation.  Those dogs which have drooping ears with narrow hairy ear canals are very likely to suffer, probably because these conditions change the temperature and humidity of the ear.  The behaviour of the individual can also play a role; those dogs which swim frequently and have moisture left in the ear canal regularly are more prone to external ear problems.  Following on from this, moisture left in the ear when it has been cleaned by human intervention (or perhaps excessive salivation and licking by another dog) can be just as damaging and the very act of overzealous cleaning can be detrimental.  Care must be exercised when plucking hairs or trying to remove the build up of wax; irritant chemicals which may be applied in order to help, may make matters worse.

Bacteria are present normally in low to moderate numbers in the ear canal, and it is not thought that the presence of bacteria alone is a predisposing cause of otitis externa.  However, when other factors allow the bacterial population to multiply, control of this infection is important.  Similarly, yeast or fungal infections can be detrimental when well established in the ear canal.  Mixed yeast and bacterial infections are common.  The presence of ear mites is a frequent finding in canker.  Ear mites feed mainly on blood and lymph and are white pinhead size parasites which run away from the light.  They are easily seen with the aid of an otoscope (an instrument used for examining the ear), but may not be otherwise demonstrable.  Tumours in the ear are not uncommon.  Some are relatively benign, others may be malignant, but their presence alone can, once again, affect the microenvironment in the ear canal and so lead to problems.  Foreign bodies, however, usually lead to trouble because of the irritation they cause.  A major predisposing factor is allergy.  It must be remembered that the lining of the ear canal is simply an extension of the skin and that many processes which affect the skin can thus cause ear disease.  Allergies to food or natural environmental constituents such as pollens, house dust, house dust mites and mould must be considered, especially in cases of chronic otitis externa.   Most other causes outlined above do not have breed or age predisposition, but allergies to environmental factors are often seen in certain breeds, such as the West Highland terrier, the German shepherd and the golden retriever (though any breed can be affected) and symptoms usually develop between one and four years of age.

The usual signs of otitis externa include head shaking, possibly with a head tilt, and scratching of the ear.  There may be an unpleasant aroma originating either from the ear alone, or if the otitis externa is part of a wider skin problem, the whole dog may be smelly.  There may be pain, which can be intense at times, making further investigation difficult, but if the dog will tolerate examination, the ear may be very inflamed and there may be some form of exudate(discharge )  . Where wax alone is in excess, the exudate is often thick and black, but it can be more liquid and purulent (containing pus) where infection has established.  Examination with an otoscope is essential to try to ascertain generalised problems.  Swabs may have to be taken to establish the presence of yeasts or bacteria, and in the latter case, establish what sort of bacteria.  This will allow the veterinary surgeon to choose the correct antibiotic.

Treatment in certain cases may be obvious.  Removal of a foreign body often resolves the problem as quickly as it started, and the use of correct antibacterial, antiparasitic or antifungal agents are important.  Judicious cleaning and plucking to remove excess wax and hair is also advised, but as mentioned above, excess vigour is contraindicated.  Other concomitant disease factors, such as allergies, must be treated.  In certain cases surgery is required.  The presence of a growth is an obvious example.  However, when the inflammation of the ear canal has become a chronic process, the lining of the canal usually becomes very thickened.  This in itself predisposes to further problems.  In such cases medical treatment may be insufficient and a variety of surgical techniques can be employed.  Perhaps one of the commonest is to remove the outside wall of the ear canal (leaving the ear flap or pinna alone) so allowing better drainage and exposure of the ear.  The ear can be cleaned more easily and the microenvironment is vastly improved.  Occasional medical treatment may still be required, but the dog is usually much happier and free from pain and irritation.

One major problem that I face as a veterinary surgeon is that clients may ask for a repeat prescription of ear drops because their dog’s ear is causing him trouble again.  In view of the vast array of different problems which can lead to otitis externa as outlined above, and especially if the last treatment was many months ago, I often have to suggest that it is in the dogs’ best interests to re-examine the ear and establish the exact nature of the latest problem.