Ear disease (‘canker’, otitis externa) is a common, recurrent problem in many dogs, and some cats. Treating the secondary infections will often result in only a short to medium term resolution. Recurrence is very likely unless the primary cause is detected & treated.

The ear(s) may be inflamed only, or inflamed and infected with any combination of yeast, round or rod-shaped bacteria, and/or with parasites.

By examining a stained ear wax preparation, I can immediately diagnose and ‘stage’ the degree of infection and inflammation. This allows us to decide on more specific diagnostic tests and targeted treatments. It also provides me with an accurate method of monitoring the response to previous, recent treatments.

The factors, causing ear canal inflammation & infection, can be divided into three categories - primary, predisposing & perpetuating – listed below. Examples of the most common causes are given:

Primary causes
These factors directly induce ear inflammation (otitis externa):
• Hypersensitivity Atopic dermatitis (the most common cause)
• Adverse food reactions (food allergy or dietary intolerance)
• Parasites Ear Mites Otodectes cynotis
• ‘Fox’ mange Sarcoptes scabiei
• Microorganisms ‘Ringworm’ Microsporum canis (Dermatophytosis) etc.
• Foreign bodies Grass seeds
• Keratoseborrhoeic Hypothyroidism
• Local Glandular disorders
• Autoimmune diseases
• Viral infections

Predisposing factors
These increase the risk of development of ear disease but do not directly induce it:
• Conformation
• Excessive moisture ‘Swimmer’s ear’
• Excessive cerumen (wax)
• Treatment effects
• Obstructive disease
• Systemic disease

Please note the first factor, conformation of the ear, does not directly cause ear disease. This is a common misconception. If this was true then all dogs with large, floppy, and/or hairy ears would have recurrent ear infections.

Perpetuating causes
These factors prevent resolution of the disease.

• Bacteria
Staphylococcus intermedius Pseudomonas sp.

• Yeast
Malassezia pachydermatis

• Progressive pathological changes (from chronic inflammation and recurrent infections)

• Otitis media (middle ear disease)

Therefore the more infections that a patient undergoes the more difficult it may be to reverse the progression of the ear disease.

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	Canine Malassezia Otitis, secondary to Atopic dermatitis Budding yeast cells attached to surface skin cells from an ear wax smear examined in the consultation. Yeast overgrowth causes recurrent, malodourous, itchy ear infections often the primary cause is allergies, especially Atopic dermatitis.
	Canine Pseudomonas Otitis, secondary to Atopic dermatitis Reproducing rod-shaped bacteria and white blood cells from an ear wax smear examined in the consultation. This troublesome, painful, secondary bacterial infection can be difficult to cure especially if the underlying cause is not treated.
	Feline Trombiculiasis This seasonal larval mite infestation causes intense irritation in cats, dogs and even humans! A close-up of this cat’s ear margins showing the alopecia, thickening and crusting.
	Pinnal Thrombovascular Necrosis, secondary to Feline GIT Lymphoma The unusual frostbite-like appearance of this cat’s eartips was caused by a rare reaction to an internal disease. The cause of this vasculitis was a resectable intestinal tumour, diagnosed by non-invasive ultrasound scanning. Removing the tumour then resolves the eartip necrosis.