What causes ear infections (otitis externa) of pets?

Bacteria and yeast are the types of organisms that most commonly cause ear infections in pets. Most infections result from an overgrowth of organisms that normally live in the ear canal without causing trouble. Infections usually only develop when the ear canal is otherwise diseased.

A wide variety of problems can lead to ear infections, including allergies, hormonal imbalances and foreign bodies (i.e., grass seeds). To properly treat and help prevent recurrence of infection, your veterinarian may investigate some of these causes.

How are ear infections diagnosed?

Pets with ear infections often have visible discharge, may scratch at their ears or shake their heads and otherwise display discomfort. When the problem progresses from inflammation to infection with bacteria or yeast, a strong odor often develops. Yeast infections (Malassezia otitis) are the most common, especially in dogs with underlying allergies. A variety of bacteria can infect pets’ ears, and these tend to become harder and harder to treat with repeated or chronic infections. Your veterinarian will perform an otoscopic examination of the ears and may perform an ear swab and microscopic examination to look for the type and abundance of these organisms. Due to the rising prevalence of antibiotic-resistant bacteria, a culture and a susceptibility test may also be recommended to aid in the selection of an effective treatment.

How are ear infections treated?

Most ear infections are treated with a combination of a topical medication and an ear cleaning solution. This will vary with the type and severity of infection. To maximize the effectiveness of topical ear medications, the ear canal needs to be cleaned of debris. This may require a thorough cleaning by your veterinarian. For severe infections or infections of deeper structures of the ear canal, oral medications, including antibiotics or antifungal drugs, may be used. Any underlying cause that might be uncovered also needs to be addressed.

What can you do to protect your pet from ear infections?

If your veterinarian identifies a medical condition predisposing your pet to ear infections (most commonly allergies), it needs to be managed. While any dog can acquire an ear infection, certain breeds are predisposed to ear infections including Basset Hounds, Beagles, Bulldogs, Cocker Spaniels, Golden Retrievers, Labrador Retrievers, Lhasa Apsos, Poodles, Pugs, Shar Peis and Springer Spaniels. It is especially important in these breeds to notify your veterinarian if you notice head shaking, pain when touching the ears or any unusual odor or buildup in the ear canals, all of which can be signs of an ear infection.