Understanding the Three Types of Ear Infection
Ear infections in dogs are classified according to how deep within the ear the infection has taken hold. Recognising the distinction matters because the deeper the infection, the more serious the implications and the more involved the treatment.
Otitis externa refers to infection of the outer ear canal — the most common form and the one most owners will encounter. Otitis media involves the middle ear, typically reached when an outer infection progresses inwards or when the eardrum ruptures. Otitis interna affects the inner ear and can lead to permanent damage including balance problems and deafness. Most cases start as otitis externa, which is why catching and treating infections early is so important.
Yeast Infections: Malassezia Pachydermatis
The most frequently diagnosed cause of canine ear infections is the yeast organism Malassezia pachydermatis, which is normally present on healthy skin in small numbers. Problems arise when conditions in the ear canal shift — typically due to increased moisture, warmth, or a disrupted skin barrier — allowing the yeast to multiply beyond normal levels.
Yeast ear infections have a fairly recognisable presentation. The discharge tends to be brown or dark reddish-brown, with a consistency somewhere between waxy and greasy. The odour is distinctive — often described as musty, yeasty, or reminiscent of stale bread. The affected ear is usually itchy, and dogs may shake their head frequently or rub the ear against furniture and flooring. In chronic cases, the skin of the ear canal can thicken and become scarred, narrowing the canal and making future infections more likely.
Treatment involves antifungal ear drops, and in moderate to severe cases an oral antifungal medication may also be prescribed. Addressing the underlying reason for the overgrowth — such as allergies or a structural ear conformation — is essential to prevent recurrence.
Bacterial Infections: Pseudomonas and Staphylococcus
Bacterial ear infections can develop on their own or alongside a yeast infection, and they are generally more painful than yeast infections alone. The two most commonly involved bacteria are Staphylococcus pseudintermedius, a gram-positive organism that tends to respond well to standard antibiotics, and Pseudomonas aeruginosa, a gram-negative bacterium that is notorious for being difficult to treat due to antibiotic resistance.
Bacterial infections tend to produce yellow or green discharge, which may be thick or pus-like. The ear is often very painful to touch, and dogs may flinch or cry when the ear is examined. Severe bacterial infections can cause the ear canal to become swollen, red, and almost completely closed. Pseudomonas infections in particular can develop a distinctive sweet or fruity odour that differs from yeast-related smell.
Diagnosis requires a cytology swab — your vet will examine a sample of the discharge under a microscope to identify the organism. In recurrent or resistant cases, a bacterial culture and sensitivity test is necessary to determine which antibiotic will be effective. This step is crucial when Pseudomonas is suspected, as inappropriate antibiotic use can worsen resistance.
Ear Mites: Otodectes Cynotis
Ear mites are a parasitic cause of ear irritation more commonly associated with cats, but dogs can certainly be affected, particularly puppies and dogs with regular contact with cats. The responsible organism, Otodectes cynotis, lives in the ear canal and feeds on skin debris.
The discharge produced by an ear mite infestation is characteristically dark brown, dry, and crumbly — often compared to coffee grounds. The ears are intensely itchy, and affected animals may scratch so vigorously that they cause self-inflicted wounds around the ear and neck. Unlike yeast or bacterial infections, ear mites are highly contagious between animals in the same household, so all pets should be treated simultaneously even if only one appears symptomatic.
Treatment with a veterinary-prescribed antiparasitic product is very effective. Over-the-counter preparations are available but may be less reliable — it is always worth having a vet confirm the diagnosis via otoscopy or microscopic examination of a swab before committing to treatment.
Polyps and Tumours: When One Ear Is Affected
When a dog develops an ear problem in only one ear, and particularly when that ear fails to respond to standard treatment, a physical cause within the ear canal should be considered. Inflammatory polyps, benign growths, and tumours can all obstruct the ear canal, create a warm moist environment that encourages infection, and cause discharge or pain that mimics a straightforward infection.
The key clinical clue is unilateral presentation — one ear persistently affected while the other remains normal. Vets will typically recommend advanced imaging such as CT scanning alongside otoscopy to evaluate the extent of any mass, particularly before committing to surgery. Some growths are entirely benign and straightforward to remove; others require biopsy and more extensive intervention. Unilateral ear disease that does not resolve should always prompt a more thorough investigation.
Predisposed Breeds
Certain breeds are significantly more prone to ear infections than others, largely due to ear anatomy and coat characteristics. The most commonly affected include:
- Cocker Spaniels — heavy, pendulous ears that trap moisture and restrict airflow
- Labrador Retrievers — enthusiasm for water combined with relatively narrow ear canals
- Poodles and Doodle crosses — hair growing within the ear canal that can block drainage and harbour bacteria
- Basset Hounds — long floppy ears with poor air circulation
- Shar-Peis — naturally narrow and often stenotic ear canals
Owners of these breeds should make ear inspection a routine part of weekly grooming and should ask their vet whether preventative ear cleaning is appropriate for their specific dog.
What Never to Do: Cotton Buds
One of the most important things to understand about dog ear care is that cotton buds should never be inserted into the ear canal. Despite seeming like an intuitive cleaning tool, cotton buds push debris deeper into the canal rather than removing it, and they carry a significant risk of damaging the delicate structures of the ear, including the eardrum. Cleaning should be performed using a veterinary-approved ear cleaner applied gently into the ear opening, with the ear then massaged at the base to help loosen debris, followed by allowing the dog to shake its head.
If you have any doubt about whether your dog's ears look or smell normal, a veterinary examination is always the right first step. Ear infections treated early resolve far more quickly and are far less likely to become chronic or to progress to deeper structures.