Dog ear infections: signs, causes and veterinary care

Dogs with ear infections often shake their heads or scratch at their ears more than usual. You may notice a strong, unpleasant odor coming from one or both ears. The ear canal may appear red or swollen, and there may be a dark, waxy discharge or pus visible.

Some dogs also tilt their head to one side, seem off-balance, or become sensitive when their ears are touched. In severe cases, hearing loss or facial nerve involvement can occur if the infection is left untreated for an extended period.

Otitis externa refers to inflammation of the outer ear canal, extending from the ear canal opening to the eardrum. It is the most frequently diagnosed ear condition in dogs and can be caused by bacteria, yeast, allergies, foreign bodies, or anatomical factors such as heavy, floppy ears that trap moisture.

Certain breeds — including Cocker Spaniels, Labrador Retrievers, and Basset Hounds — are predisposed to recurrent ear infections due to their ear shape and hair growth patterns inside the ear canal. Dogs with narrow ear canals may also be at higher risk.

The two most common types of ear infections in dogs are yeast (Malassezia) and bacterial. Yeast infections tend to produce a distinct musty odor and thick, waxy discharge. Bacterial infections may produce a more pus-like or watery discharge and can be more painful.

Sometimes both organisms are present simultaneously. A veterinarian can identify the causative organism through a simple ear cytology — a swab examined under a microscope — which allows targeted treatment rather than relying on broad-spectrum medications that may not be fully appropriate.

Allergies are one of the most common underlying reasons dogs develop recurrent ear infections. Environmental allergies (atopic dermatitis) and food sensitivities cause inflammation in the skin, and the ear canal — which is lined with skin — is frequently affected.

Dogs with untreated allergies often cycle through repeated ear infections even after appropriate treatment of each individual episode. Addressing the underlying allergy is important for long-term ear health and may involve allergy testing, medication, or dietary trials guided by your veterinarian. Routine wellness care helps detect these issues before they become chronic.

Ear mites (Otodectes cynotis) are small, contagious parasites that live in the ear canal and feed on skin debris. They are most commonly seen in puppies and dogs that have close contact with other animals, including cats.

Signs of ear mites include intense head shaking, scratching, and a dark, crumbly discharge that often resembles coffee grounds. Because ear mites are highly contagious between pets, all dogs and cats in the household may need to be treated simultaneously. Your veterinarian can confirm the presence of mites with an otoscopic examination.

Ear cytology is a quick, in-clinic diagnostic tool. A swab is taken from the ear canal, stained, and examined under a microscope. This allows the veterinarian to determine whether the infection is caused by yeast, bacteria, or both — and to identify the type of bacteria present.

This information is essential for selecting the most effective treatment. Using the wrong medication may not resolve the infection and can contribute to antibiotic resistance or prolonged discomfort for the dog.

Dogs that experience frequent ear infections may have an underlying condition that predisposes them to ear disease. Common contributing factors include untreated allergies, anatomical features of the ear canal, hormonal imbalances, and over-cleaning of the ears which disrupts the normal skin barrier.

A thorough evaluation — including allergy assessment, cytology, and potentially blood work — can help identify the root cause. A management plan that addresses the underlying issue, rather than just treating symptoms, is the most effective approach for reducing the frequency of future episodes.