Ear infections are one of the most common reasons dogs are brought to the vet. They can also be incredibly frustrating when they keep returning.
If your dog's ears improve with treatment, only to flare again a few weeks or months later, it does not necessarily mean the medication failed or that you did something wrong. More often, the infection settled but the reason the ear became inflamed in the first place is still there.
What is actually happening inside the ear?
Otitis externa means inflammation of the external ear canal. Despite commonly being called an ear infection, the inflammation often starts before there is any infection at all.
Yeast and bacteria can be found in healthy canine ears. Problems begin when something changes the ear canal and allows these organisms to multiply beyond normal levels.
Allergies are a common starting point. Ear conformation, excessive moisture, foreign bodies and ear mites can also contribute. Once the ear has been inflamed repeatedly, the canal may become thickened, narrowed and less able to clear wax naturally. These changes make future episodes more likely and increasingly difficult to treat.
A major 2023 clinical review describes recurrent ear infections as secondary problems. In other words, the yeast or bacteria are rarely the whole story. Successful long-term treatment depends on finding and managing what allowed them to overgrow.
Signs of an ear infection
Dogs with ear disease may show:
- Head shaking
- Scratching at the ear
- Rubbing the side of the face against furniture or the floor
- Redness or swelling inside the ear
- Wax or discharge
- A strong or unusual smell
- Pain when the ear is touched
- Reluctance to have the head handled
Discharge colour alone cannot tell you whether the problem is yeast or bacteria. Brown discharge is often associated with yeast, but it can also occur with bacterial or mixed infections. Smell is not a reliable diagnostic test either.
A head tilt, loss of balance, walking in circles, vomiting, facial drooping or rapid flicking movements of the eyes may mean the middle or inner ear is involved. These signs need prompt veterinary assessment.
Why the ear swab matters
During an ear examination, your vet will usually examine the canal with an otoscope and take a sample of the discharge. That sample is stained and examined under a microscope, a test called ear cytology.
Cytology can show whether yeast, round bacteria, rod-shaped bacteria or inflammatory cells are present. It also helps your vet decide whether the ear needs an antifungal, an antibacterial, an anti-inflammatory medication or a combination.
This is why choosing drops based only on how the ear looks is unreliable. Two ears can produce similar brown discharge while having quite different problems.
Cytology is also useful at rechecks. A dog may stop scratching before the inflammation and microbial overgrowth have fully resolved. Feeling better is encouraging, but it does not always mean treatment is finished.
Does every recurrent infection need a culture?
No. A culture is not automatically the next step for every chronic ear problem.
Culture may be helpful when cytology shows unusual organisms or rod-shaped bacteria, when middle-ear infection is suspected, when systemic antibiotics may be needed, or when an appropriately treated infection is not improving.
However, culture does not replace cytology. Susceptibility results from a laboratory do not always predict how an organism will respond to medication applied directly into the ear canal. The amount of discharge, inflammation, narrowing and biofilm within the ear can all affect treatment.
Antimicrobial resistance is still an important concern, particularly after repeated or poorly targeted antibiotic exposure. A large 2025 study of canine ear isolates found substantial resistance among several important bacterial groups. This is another reason not to use leftover ear drops or repeat antibiotics without examining the ear first.
Why allergies cause recurring ear problems
Allergic skin disease is one of the most common underlying causes of recurrent otitis. Environmental allergies are seen more often, although food allergy can produce a very similar pattern.
The ear canal is lined with skin. In an allergic dog, that skin can become inflamed just like the skin between the toes, under the legs or around the face.
Early allergic ear disease may cause little more than redness and mild wax production. Over time, the inflammation causes more discharge, swelling and thickening. Normal movement of skin and wax out of the canal becomes less effective. The result is an ear that stays warmer, damper and easier for yeast and bacteria to overgrow in.
A 2024 review found that allergic inflammation can alter several of the ear canal's normal protective features. The precise role of the ear microbiome is still being studied, but the clinical message is already clear: controlling infection without controlling inflammation leaves the ear vulnerable to another flare.
Some allergic dogs have itchy paws, recurrent skin infections or redness elsewhere. Others show very little outside the ears. Recurrent otitis can sometimes be the first, or even the only obvious, sign of allergic skin disease.
Could it be a food allergy?
Yes, although food allergy should not be assumed simply because a dog has recurring ear infections.
When food allergy is genuinely suspected, the reliable way to investigate it is a properly conducted elimination diet followed by a food challenge. Blood, saliva and hair tests have not been shown to diagnose canine food allergy reliably. A 2019 diagnostic study found that saliva and serum food-antibody tests could not reliably distinguish food-allergic dogs from healthy dogs.
Changing foods repeatedly is not the same as performing a diagnostic diet trial. The diet needs to be selected carefully, fed exclusively and continued for long enough to give a meaningful answer. This is best planned with your vet.
Track what matters. A simple weekly check-in on your dog's energy, appetite, comfort, stools, sleep, and thirst makes changes far easier to spot.
When only one ear is affected
Allergic ear disease often affects both ears, although one may be worse than the other. A persistently one-sided problem deserves a closer look.
Possible causes include:
- A grass seed or other foreign body
- A polyp or growth within the canal
- Localised narrowing or scar tissue
- Disease behind the eardrum
- Chronic changes left by an earlier infection
A painful or severely narrowed ear may need to be examined under sedation. In some cases, imaging or a biopsy is needed. Repeating the same drops will not solve a problem caused by a foreign body or an obstructing mass.
Two similar dogs, but two different problems
Consider two five-year-old Labradors with red, discharging ears.
One develops an isolated episode after several days of swimming. The infection clears, the ears are dried carefully after future swims, and the problem does not return.
The other has had four episodes in a year and also licks his paws. His ears improve each time drops are used, but they never stay settled for long.
The first dog may simply have needed treatment and better moisture control. The second needs an allergy investigation and a longer-term plan. Giving another course of drops without addressing the allergy is unlikely to change the pattern.
What should treatment involve?
Treatment should be based on what is found during the examination and on cytology. Depending on the ear, this may include cleaning, topical medication, pain relief and treatment aimed at reducing inflammation.
There is no single treatment length that suits every dog. Mild, uncomplicated cases may improve quickly. Chronic, narrowed or severely inflamed ears often take longer and need rechecks.
For recurrent cases, treatment has two jobs:
- Settle the current inflammation and microbial overgrowth.
- Reduce the chance of the next episode by managing the underlying cause.
That longer-term plan may involve allergy management, a carefully chosen cleaning schedule, moisture control and, in some dogs, intermittent anti-inflammatory ear treatment prescribed by your vet. Recent studies published in 2025 and 2026 support this proactive approach, although the exact plan still needs to be tailored to the individual dog.
Cleaning the ears safely
Not every dog needs regular ear cleaning. Cleaning too often, using the wrong product or handling an already painful ear can create more irritation.
If your dog is prone to ear problems:
- Use a cleanser recommended by your vet.
- Ask how often it should be used. More is not necessarily better.
- Dry the outer ears after swimming or bathing.
- Do not insert cotton buds into the ear canal.
- Avoid water, vinegar, hydrogen peroxide, essential oils and homemade mixtures unless your vet has specifically advised otherwise.
- Do not use old prescription drops left over from a previous infection.
Routine deep plucking of ear-canal hair is not necessary for every dog and can cause inflammation. If excessive hair is obstructing the canal or preventing treatment from reaching the skin, careful removal may be helpful under veterinary guidance.
If your dog is due to have the ears examined, avoid cleaning them immediately beforehand unless your vet asks you to. Cleaning can remove material needed for cytology and make the findings harder to interpret.
Questions owners often ask
Can I try an over-the-counter cleaner first?
If the ear is red, painful, smelly or producing abnormal discharge, it should be examined. A cleaner may remove some wax without treating the inflammation or microbial overgrowth. Some products are also unsafe if the eardrum is damaged.
Why does the same ear keep becoming infected?
One ear may have more severe chronic change than the other, but a repeatedly one-sided problem can also point to a foreign body, growth, narrowing or middle-ear disease. Tell your vet that it is always the same ear.
Could it still be an allergy if my dog has no skin problems elsewhere?
Yes. Ear inflammation can appear before more typical allergy signs become obvious, and in some dogs the ears remain the main problem.
Do floppy ears cause infections?
Floppy ears can reduce ventilation and retain moisture, but ear shape alone usually does not create an infection. It is better thought of as a predisposing factor. Allergic inflammation, swimming or another trigger is often present as well.
What to Do This Week
Lift your dog's ear flaps this week and look for redness, discharge, swelling or a strong smell. If your dog has a history of ear problems, schedule a recheck with your vet before symptoms return, and ask whether an allergy or moisture management plan is appropriate.
When to See a Vet Urgently
Seek prompt veterinary care if your dog has a head tilt, loss of balance, walking in circles, vomiting, facial drooping, rapid flicking eye movements, severe pain, significant swelling, or if the ear is bleeding or producing pus. These signs may indicate middle- or inner-ear involvement and should not be waited on.
This article is for educational purposes only and does not replace professional veterinary advice. If your dog is unwell, please consult your veterinarian.
About the Author
Dr Kelly Yeo graduated from the University of Melbourne in 2009 and has extensive experience in companion animal medicine, with a special interest in geriatric care, chronic disease management, palliative care, and canine longevity.
Her work focuses on helping dogs live longer, healthier, and more comfortable lives through early detection, thoughtful nutrition, practical preventive care, and compassionate support for owners.
