What causes ear infections in dogs?

Ear infections in dogs are common, uncomfortable, and something every dog lover should recognize early. I typically see owners underestimate how quickly a partly blocked or wet ear can turn into a painful, smelly problem that affects a dog’s hearing and behavior. Understanding the likely causes, what to watch for, and how to respond can save your dog needless discomfort and reduce repeated vet visits.

How ear infections affect your dog’s comfort, hearing and behavior

Ear infections matter because they directly affect a dog’s comfort, sound perception, and long-term ear health. A dog with a sore ear may stop playing, shy away from touch, or suddenly scratch and shake its head a lot. Left unchecked, repeated infections can scar the ear canal, narrow it, and make future problems more likely; that can mean ongoing treatment costs and, in some cases, surgery. For families who swim, bathe, groom, or share space with dogs that have allergies, ear trouble is a common recurring stressor.

There are everyday scenarios where owners notice trouble: a Labrador that comes out of the lake shaking, a poodle after a clip when the groomer has plucked ear hair, or a bulldog with chronically reddened ears during pollen season. Certain breeds and lifestyles put dogs at higher risk—breeds with long, floppy ears or very hairy ear canals, dogs that live in humid climates, and those with chronic skin allergies. When curiosity about a head tilt or a scratch escalates into intense pain, drainage, or neurologic signs, what began as routine care can become urgent veterinary work.

What typically triggers ear infections in dogs

The short version for busy owners: most ear infections come from a few common problems that change the ear’s normal balance. Bacterial overgrowth—often involving Staphylococcus species or, less commonly, Pseudomonas—may drive strong-smelling, thick discharge. Yeast overgrowth, usually Malassezia, gives a sweet or musty odor and brownish greasy debris. Ear mites, more typical in puppies and multi-pet households, cause intense itch and dark crumbly debris. Other frequent contributors include allergies (food or environmental), trapped foreign material like grass awns, and retained moisture after swimming or bathing that allows microbes to flourish.

• Bacterial infections (e.g., Staphylococcus, Pseudomonas)
• Yeast overgrowth (Malassezia)
• Ear mites (Otodectes cynotis)
• Allergies, foreign bodies, and moisture-related problems

Inside the canine ear: structure and normal function

To understand why infections happen, it helps to picture the ear’s basic structure. The visible flap, or pinna, funnels sound into the vertical then horizontal ear canal. In dogs the canal is long and L-shaped, which means debris and moisture can sit out of sight. The normal ear environment is warm and relatively dark—conditions that may favor microbes if the usual checks and balances shift.

The ear produces cerumen (earwax) that traps dirt and has mild antimicrobial properties; that is part of the ear’s first line of defense. Behind the ear canal lies the eardrum (tympanic membrane) and the middle ear; infections limited to the canal are termed otitis externa, while deeper infections involve the middle ear. A healthy ear also has local immune cells and a balanced community of bacteria and yeasts—the ear microbiome—that helps keep potential pathogens in check. Disruption of that balance—through moisture, injury, or allergy—makes infection more likely.

When infections are most likely to develop — common scenarios

Timing and environment often reveal why an ear flares up. I commonly see infections appear after a dog swims or gets a bath because water that remains in the ear can lower oxygen and allow yeast and bacteria to multiply. Seasonal allergy flares—hayfever or atopic dermatitis—often coincide with recurrent otitis because the skin of the ear becomes inflamed, itchy, and secondarily infected. Grooming events that involve plucking ear hair or aggressive cleaning can also irritate the canal and open the door to infection.

Breed anatomy plays a role: dogs with long, pendulous ears (like spaniels) have less airflow into the canal, and breeds with very hairy ear canals or narrow openings (poodles, cocker spaniels) may trap moisture and debris. Age matters too—young dogs are more likely to have ear mites or foreign bodies, while middle-aged dogs often show allergy-linked infections. Environmental humidity, household bathing frequency, and even the dog’s behavior around scratching and shaking all influence when and how infections appear.

Red flags: symptoms that require prompt veterinary attention

Not every ear itch is an emergency, but certain signs suggest the problem is severe or has spread. Intense head shaking, persistent pawing at the ear, and obvious pain are signals that a veterinary exam is warranted. A strong, foul odor; bloody or thick colored discharge; or very swollen, hot ears may suggest a deep bacterial infection or an early abscess. Changes in hearing, a pronounced head tilt, drooping of the facial muscles on one side, or stumbling can indicate the infection has advanced toward the middle or inner ear and requires prompt attention.

Recurrent infections—or infections that do not improve with an initial course of treatment—are also red flags. Repeated flare-ups suggest an underlying cause such as an allergy, endocrine disease, or structural problem that needs addressing. If you see any neurologic signs, dramatic changes in behavior, or if the dog becomes febrile, seek veterinary care urgently; these are not things to wait out at home.

What to do right away if you suspect your dog has an ear infection.

If you suspect an ear infection, the safest first step is to avoid making the ear worse. Do not insert cotton swabs or any object into the ear canal; that risks pushing debris deeper or damaging the eardrum. Instead, gently part the ear flap and look inside with a flashlight—photograph what you see to show the veterinarian. Note smell, color of discharge, and how your dog reacts to touch. I often find these simple observations help the vet decide how urgently the dog needs to be seen.

If your veterinarian has previously shown you a specific ear cleaner and you’ve been instructed to use it for flare-ups, you may apply it as directed while arranging a clinic visit. Otherwise, avoid over-the-counter remedies without professional guidance. Call your veterinarian to book an exam; if your dog has intense pain, facial droop, balance problems, or is unwilling to eat, seek emergency care. In the clinic the vet will likely examine the canal, perform ear cytology (a quick microscope check of microbes), and decide on topical or systemic treatment based on the findings.

At-home routines that reduce the risk of ear trouble

Simple routines can reduce how often a dog gets ear trouble. Drying ears thoroughly after swimming or bathing is one of the single most effective measures; gently blot the outer ear and allow the ear to air for a few minutes. During routine grooming, check the ears for redness, abnormal odor, or debris; catching slight changes early lets you seek advice before a full infection sets in. For dogs with known allergies, managing the allergy—through diet trials, environmental control, or veterinary allergy therapies—often reduces ear disease frequency.

Training your dog to tolerate ear handling also pays dividends. Short, positive sessions where the ear is touched calmly, followed by a treat, make future exams and cleanings much easier and less stressful for both of you. If ear hair is a problem in certain breeds, ask your vet or an experienced groomer about safe options rather than attempting to pluck hair yourself; improper hair removal can traumatize the canal.

Safe tools and products vets recommend for ear care

Use tools that help rather than harm. Vet-recommended ear cleaning solutions and drying sprays can be useful after water exposure or as maintenance when advised by your veterinarian; these products are formulated to restore pH and remove debris without irritating the ear. For outer-ear cleaning, soft cotton balls or gauze can gently wipe away visible wax and discharge—avoid Q-tips or anything that goes into the canal. For active swimming dogs, lightweight ear covers or neoprene hearing protectors may reduce water entry, though they are not perfect prevention.

Home otoscopes sound helpful but can be risky without instruction; if you plan to use one, ask your veterinarian for a demonstration first to avoid accidental damage. Keep a small supply kit with a light, camera or phone for photos, a clean towel, and the contact info for your vet—having these ready makes a quick response easier when a problem starts.

Experts to consult — veterinarians, dermatologists and trusted resources

When in doubt, rely on veterinary professionals and respected reference centers. Your primary care veterinarian is the best first contact; if ear disease is complicated or recurrent, a veterinary dermatologist or an ENT-focused specialist may add valuable diagnostic tools like culture and sensitivity tests, advanced imaging, or surgery. Veterinary nurses and certified groomers can help with routine care and training for ear handling. University veterinary hospitals and specialist referral centers often publish client-facing guidance that explains diagnostics and treatment options in clear terms.

References and further reading

• Merck Veterinary Manual: “Otitis Externa in Dogs” — Merck Veterinary Manual, section on canine ear disease
• Miller WH, Griffin CE, Campbell KL. Muller and Kirk’s Small Animal Dermatology, 8th Edition. Elsevier. Chapter on canine otitis
• Cornell University College of Veterinary Medicine: “Ear Disease (Otitis) in Dogs” client information pages
• University of California, Davis Veterinary Medicine: “Otitis Externa in Dogs” — VMTH client handouts and resources
• Royal Veterinary College (RVC) Ophthalmology & Otology resources: “Canine Ear Disease” clinical guides
• PubMed: search for peer-reviewed reviews on “canine otitis externa” for up-to-date research and treatment studies