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 bacteria 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 typically produce a brown to dark brown, waxy discharge with an unpleasant 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 moister discharge of most bacterial or yeast infections. Ear mites are especially common in cats, are seen more often in young animals such as kittens and puppies, and spread between in-contact animals.
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 such as a grass seed lodged in the ear canal usually causes head shaking and scratching at the ear, often starting suddenly. Inflammatory discharge can follow, particularly if secondary infection develops. Foreign bodies usually affect one ear, which can help distinguish them from conditions that affect both ears.
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. With a foreign body, head shaking and scratching usually start suddenly, and discharge can follow, particularly if secondary infection develops. 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 typically produce a dark brown, coffee-ground-like discharge in the ear canal, especially in cats.
Squamous Cell Carcinoma of the Pinna in Cats
Pinnal squamous cell carcinoma affects the ear flap, usually the sparsely haired ear tips, rather than the ear canal. Crusting, oozing and ulceration of the ear tip can be mistaken for discharge or odour from the ear.
Otitis Interna
Otitis interna usually follows spread of infection from the middle ear, and middle ear infection often begins as otitis externa with discharge and odour from the ear canal. Inner ear involvement causes a head tilt, loss of balance and flicking eye movements (nystagmus).
Otitis Media
Otitis media usually arises when infection spreads from the external ear canal through the eardrum, so discharge and odour from the canal often accompany it. The eardrum can be intact and look normal, so the absence of discharge does not rule otitis media out.
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.
When ear discharge is accompanied by a head tilt, loss of balance, flicking eye movements, a drooping lip or face, or a drooping eyelid, these signs suggest the middle or inner ear is involved, and how deep an ear infection has spread cannot be judged by looking into the ear at home.
Noting the characteristics of ear discharge (its colour, consistency and 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 animal's ears normally look and smell like provides a baseline against which changes can be measured.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS