Ear Infections in Dogs

By Florence Chong

Ear infections are common in dogs and are frequently seen at our grooming salon. They cause notable discomfort, and the J-shaped ear canal makes dogs more prone to these infections than humans.

Most canine ear infections affect the external ear canal — or otitis externa. (Otitis media and otitis interna involve the middle and inner ear, respectively.) This article discusses the science and treatment of otitis externa, the most common ear infection in dogs.

A dog’s ear canal normally contains yeast and bacteria, but an overgrowth of these can lead to otitis externa (an ear infection).

Overgrowth of yeast or bacteria usually results from changes in the ear canal environment that encourage secondary infections. Contributing factors may include:

• Allergic reactions — whether to specific foods or environmental allergens.
• The anatomical configuration of the ear — such as long, pendulous ears.
• Presence of foreign material within the ear canal.
• Endocrine disorders, for example, hypothyroidism.

If the cause isn’t treated and the ear infection persists, it can become chronic and lead to complications such as hearing loss or ear hematomas (swelling of the ear flap from frequent shaking).

Yeast and Fungal Ear Infections:

Yeast and fungal ear infections in dogs are commonly caused by the excessive growth of Malassezia pachydermatis. This organism is typically found in low levels but may multiply and lead to secondary infection if conditions within the ear change.

Yeast thrives in moisture, so dogs with long, drooping ears or those that swim often, like Basset Hounds, are more likely to get yeast ear infections.

Causes:

Allergies to foods or environmental substances are a common factor associated with yeast ear infections in dogs.

Other chronic or hormonal conditions, including diabetes, hypothyroidism (reduced thyroid hormone levels), and Cushing’s disease, may also contribute to increased yeast growth in the ear canals.

Antibiotics can decrease beneficial bacteria, causing an imbalance that may lead to yeast overgrowth and ear infections.

Symptoms:

Yeast ear infections in dogs look similar to bacterial ones, causing head shaking, ear scratching, and a sweet or yeasty smell. Affected ears are usually red, inflamed, with thick dark wax, and may cause head tilting and sensitivity.

The veterinarian will review your dog’s allergy history, examine the ears with an otoscope, and test for yeast. Blood or skin tests may be performed to check for other conditions such as hypothyroidism. Sedation may be required if ear pain hinders the exam.

Manage underlying causes: 

Addressing and managing factors such as allergies can help resolve and prevent yeast ear infections in dogs.

Bacterial Ear Infections: 

Most bacterial ear infections in dogs are caused by an overgrowth of Staphylococcus spp., with other culprits including Pseudomonas, Proteus, Enterococcus, Streptococcus, and Corynebacterium. Staphylococcus and Pseudomonas are especially difficult to treat due to their biofilm formation, which resists many medications.

Causes:

Bacterial ear infections in dogs commonly result from allergies, hormonal imbalances like hypothyroidism, or foreign material in the ear canal. Other risks include too much ear hair, frequent cleaning, and humid conditions.

Symptoms 

Bacterial ear infections in dogs typically present with white, yellow, or greenish discharge and a noticeable odor, distinguishing them from yeast infections. Both conditions may lead to unpleasant-smelling ears, erythema, frequent scratching, head shaking, and sensitivity when the ears are handled.

If a dog is diagnosed with a bacterial ear infection, a veterinarian may suggest a combination of treatments to address and resolve the infection, like those used for yeast ear infections.

Effectively identifying and managing contributing conditions, such as allergies, is essential for both the resolution and prevention of bacterial ear infections in dogs.