SYMPTOM
Ear discharge or odour
Visible discharge from one or both ears, which may be dark, waxy, yellowish, or bloody, often accompanied by an unusual or unpleasant smell.
Bacterial ear infection
Bacterial overgrowth in the ear canal is one of the most common causes of ear discharge. The discharge may appear yellowish, greenish, or creamy depending on the species involved, and often has a distinctly unpleasant odour. Staphylococcus and Pseudomonas are frequently encountered, with Pseudomonas producing a particularly malodorous, sometimes greenish discharge.
Yeast overgrowth
Malassezia pachydermatis can proliferate excessively in warm, moist, inflamed ear canals. Yeast-dominated infections produce a characteristic dark brown, waxy discharge with a distinctive sweet, musty odour. Yeast overgrowth is particularly common in dogs with allergic ear disease, floppy ears, or in humid environments.
Ear mite infestation
Otodectes cynotis mites produce a characteristic dark, crumbly, coffee-ground-like discharge distinct from the wetter discharge of bacterial or yeast infections. This type is more commonly seen in puppies and young dogs and is highly contagious.
Allergic ear inflammation
Allergic conditions frequently target the ears, producing increased ceruminous gland secretion and predisposition to secondary overgrowth. The initial allergic inflammation may produce excess waxy discharge before secondary infection develops. Dogs with allergic ear disease often produce more cerumen than normal even between episodes.
Foreign body reaction
A foreign object lodged in the ear canal triggers inflammatory discharge as part of the body's attempt to flush and protect the canal. This discharge may initially be thin and clear before becoming purulent as secondary infection develops. It is typically unilateral, which can help distinguish it from bilateral conditions.
Why timing matters
Early observation
When ear discharge or odour is first noticed, it indicates the ear canal environment has shifted from its normal state. Early discharge may be relatively mild — a slight increase in wax, a subtle colour change, or a faint odour. At this stage, the canal is usually still of normal diameter and inflammatory changes are superficial, making investigation and treatment more straightforward.
Later presentation
Persistent or worsening discharge over days to weeks suggests an established process unlikely to resolve spontaneously. The discharge may become more copious, change in character, or develop a more intense odour. Chronic discharge can cause secondary changes including maceration of canal skin, dermatitis of the ear flap from moisture, and canal narrowing that impairs natural drainage.
The evolution often reflects the underlying cause. Allergic ear disease produces discharge that waxes and wanes with allergen exposure. Bacterial infections may progress from mild wax to frank pus over days. Yeast overgrowth tends to produce persistent dark waxy discharge. Foreign body-related discharge is acute in onset and progressive. Monitoring changes in volume, colour, consistency, and odour over time provides valuable information.
Conditions commonly associated
Otitis Externa in Dogs
Discharge from the ear canal, sometimes accompanied by an unusual odour, is a hallmark presentation of otitis externa. The character of the discharge may vary depending on the underlying cause and the duration of the inflammation.
Atopic Dermatitis in Dogs
Atopic dermatitis frequently involves the ear canals, with allergic inflammation predisposing to secondary infections that produce discharge and odour changes.
Otitis Externa in Cats
Ear discharge and odour are common signs of otitis externa in cats. The character of discharge may vary depending on whether mites, bacteria, or yeast are involved.
Nasopharyngeal Polyps
Ear discharge can occur when polyps extend through the eardrum into the external ear canal.
Ear Mites
Ear mites produce characteristic dark brown to black, dry, coffee-ground-like discharge consisting of mite waste, dried blood, and wax.
When to explore further
When ear discharge has a purulent quality or an intensely unpleasant odour, these characteristics suggest active bacterial infection within the ear canal.
When discharge is present in both ears simultaneously, bilateral involvement often suggests a systemic predisposing factor such as allergic disease rather than a localised cause.
When ear discharge recurs after apparently successful treatment, this pattern strongly suggests an underlying predisposing factor that has not been adequately managed.
When ear discharge is accompanied by signs of pain such as vocalisation when the ear is touched or reluctance to have the head handled, the pain suggests deeper or more severe inflammation.
When the character of the discharge changes from previous episodes, this may indicate a shift in the microbial population or development of a secondary infection.
Noting the characteristics of ear discharge — its colour, consistency, odour, and whether it affects one or both ears — can provide useful information. Many owners find it helpful to gently lift the ear flap periodically to check for changes in wax quantity, colour, or smell. Understanding what the dog's ears normally look and smell like provides a baseline against which changes can be measured.
Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS