CONDITION
Otitis Externa in Dogs
Inflammation of the external ear canal, often involving bacterial or yeast overgrowth, that causes discomfort, discharge, and changes in ear-related behaviour.
Why this matters now
Otitis externa is one of the most frequently encountered conditions in canine veterinary practice, affecting dogs of all ages, breeds, and lifestyles. Certain breeds with pendulous ears, narrow ear canals, or excessive hair growth within the canal — such as Cocker Spaniels, Basset Hounds, Labrador Retrievers, and Poodles — tend to be overrepresented. The condition can occur at any time of year, though many dogs experience worsening during warmer, more humid months when the ear canal environment becomes more conducive to microbial overgrowth. Dogs that swim regularly, those with underlying allergic conditions, and those with anatomical features that restrict airflow through the ear canal are particularly susceptible.
Otitis externa often begins as mild inflammation that may resolve with appropriate attention, but without addressing the underlying cause, it frequently follows a relapsing course. Repeated episodes of inflammation can lead to progressive changes in the ear canal itself — thickening of the canal lining, narrowing of the canal diameter, increased ceruminous gland activity, and eventually mineralisation of the cartilage. These chronic changes can transform what began as a straightforward inflammatory episode into a self-perpetuating cycle. In some cases, chronic otitis externa can progress to otitis media, involving the middle ear, which introduces additional complexity.
Signals & patterns
Early signals
Head shaking or ear scratching
One of the earliest signs owners typically notice is an increase in head shaking or scratching at the ears. The dog may shake its head more frequently than usual, paw at one or both ears, or rub its head against furniture or the floor. These behaviours reflect the discomfort and irritation within the ear canal.
Ear odour
An unusual smell emanating from the ears is a common early indicator. The odour may be described as yeasty, musty, or distinctly unpleasant, resulting from the metabolic byproducts of bacteria or yeast proliferating within the warm, moist environment of the inflamed ear canal.
Visible redness inside the ear flap
When the ear flap is lifted, the visible portion of the ear canal entrance and the inner surface of the pinna may appear redder than usual. This erythema reflects the inflammatory process occurring within the canal and may be accompanied by mild warmth to the touch.
Increased ear wax or discharge
A change in the quantity, colour, or consistency of ear wax may be noticeable in the early stages. Normal ear wax is typically light brown and minimal. In early otitis, the ceruminous glands may produce excess wax that appears darker, thicker, or more abundant than usual.
Later signals
Pain on ear handling
As otitis progresses, the ears may become increasingly painful to touch. Dogs may pull away, yelp, or show defensive behaviour when their ears are examined. This pain response reflects deepening inflammation and may also indicate involvement of structures beyond the superficial canal lining.
Thickened, narrowed ear canals
Chronic or recurrent otitis can cause progressive thickening of the ear canal walls, visibly narrowing the canal opening. This change represents tissue remodelling in response to sustained inflammation and can be observed when the ear flap is lifted.
Persistent or purulent discharge
Later-stage otitis often produces more substantial discharge that may be yellowish, greenish, or dark brown, sometimes with a creamy or purulent consistency. This discharge may be visible on the ear flap, on bedding, or noticed when the dog shakes its head.
Head tilt or balance changes
If otitis externa progresses to involve the middle ear, dogs may develop a head tilt toward the affected side or show subtle changes in balance. This progression represents extension of the infection beyond the external canal.
Click to read about the biological mechanisms
How this is usually investigated
Investigation of otitis externa typically involves a systematic approach that examines both the ear itself and the potential underlying causes that initiated and maintain the inflammatory process.
Otoscopic examination
Ear cytology
Bacterial culture and sensitivity
Allergy investigation
Advanced imaging
Options & trade-offs
Management typically involves addressing the immediate infection and inflammation while simultaneously identifying and managing any underlying predisposing factors.
Topical ear medications
Topical preparations applied directly into the ear canal form the foundation of treatment. These typically contain antimicrobial agents, anti-inflammatory components, and sometimes additional ingredients for pain relief. The specific formulation is guided by cytology findings.
Trade-offs: Requires owner compliance with application schedules. Some dogs develop sensitivity to certain ingredients. Duration is typically two to four weeks, and premature discontinuation is a common cause of relapse.
Ear cleaning protocols
Regular ear cleaning using appropriate solutions can help remove debris, reduce microbial load, and maintain a healthier environment. Cleaning protocols may be intensive during active infection and transition to maintenance frequency.
Trade-offs: Over-cleaning or inappropriate solutions can cause irritation. Cleaning painful ears requires gentle technique. Some solutions are contraindicated if the tympanic membrane is ruptured.
Systemic medication
Oral or injectable medications may be used alongside topical treatment in severe cases, middle ear involvement, or when topical application alone is insufficient. Systemic anti-inflammatories can reduce canal swelling to allow better topical penetration.
Trade-offs: Systemic medications carry potential side effects. Systemic antimicrobial use should be judicious to minimise resistance development.
Management of underlying causes
Identifying and addressing the primary cause — most commonly allergic disease — is essential for reducing recurrence. This may involve dietary modification, allergen management, immunotherapy, or ongoing anti-pruritic medication.
Trade-offs: Requires additional time and resources. Allergy management is typically lifelong rather than curative. Some dogs have multiple contributing factors.
Surgical intervention
In severe chronic cases with irreversible canal changes, surgical options range from lateral wall resection to total ear canal ablation with bulla osteotomy in end-stage disease.
Trade-offs: Reserved for cases not responding to sustained medical management. Recovery involves post-operative care, and hearing on the affected side may be altered.
Common misconceptions
"Ear infections are caused by not cleaning the ears enough."
Most cases of otitis externa are driven by underlying factors such as allergic disease, ear canal anatomy, or hormonal conditions rather than inadequate cleaning alone. Excessive or inappropriate cleaning can itself contribute to irritation. Dogs with healthy ears typically maintain their ear canals without regular cleaning. The focus on cleaning as a primary cause can divert attention from identifying the actual underlying driver.
"Once an ear infection clears up, the problem is resolved."
If the underlying cause remains unaddressed, recurrence is likely. Many dogs experience repeated episodes because treatment focuses on the infection rather than the reason the ear became infected. Understanding otitis as a symptom of an underlying predisposition rather than a standalone condition is essential for developing effective long-term management.
"All ear infections are the same and can be treated with the same medication."
Otitis can involve different combinations of bacteria, yeast, or both, and the specific organisms significantly influence which treatments are appropriate. Chronic infections may involve resistant organisms requiring targeted selection based on culture testing. This variability is why ear cytology is standard, allowing treatment to be tailored to the specific microbial population.
Understanding otitis externa as a condition with both immediate and underlying components can help frame the approach to managing it over time. Many owners find it valuable to learn what their dog's healthy ears look and smell like, so that early changes can be recognised. For dogs with recurrent otitis, exploring the possibility of an underlying allergic condition may offer a path toward reducing episode frequency and severity.
Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS