If your dog keeps shaking their head, scratching at one ear, or you notice a sour smell when they snuggle up, an ear infection is a likely suspect. Inflammation of the outer ear canal, called otitis externa, is one of the most common problems vets see. In a study of more than 22,000 dogs under primary veterinary care in the UK, about 7 in every 100 were diagnosed with it in a single year. [1]
Ear problems can be painful, and they tend to come back if the reason behind them is not found. Here is what owners should know.
Signs of an ear infection
Signs to watch for include: [2]
- Head shaking or rubbing the ear on furniture or the floor
- Scratching at the ear
- Redness and swelling of the ear flap or canal
- Discharge, which may be dark and crumbly, waxy, or wet and pus-like
- Scaly skin on the ear flap
- A sour or unpleasant smell
Signs vary with the cause and with how long the problem has been going on. Ear mite infections tend to be very itchy, for example, and the look of the discharge can hint at whether yeast or bacteria are involved, although only a check under the microscope confirms it. [2]
Ear pain is common, especially in badly inflamed ears. [2] A dog with sore ears may pull away when you touch their head, tilt their head, or be grumpy about being handled.
What causes ear infections?
Vets think about ear disease in layers, because there is usually more than one thing going on. A widely used framework splits the causes into primary, secondary, predisposing and perpetuating factors. [1]
Primary causes: what starts the problem
These are the triggers that first inflame the ear canal. [1][2]
- Allergies. In a study of 100 dogs with otitis externa, allergic skin disease was the most common primary cause, found in 43 of the 100 dogs. [4] Ear problems are often part of a wider itchy-skin problem. See our guide to why dogs get itchy.
- Foreign bodies such as grass awns (grass seeds). These were the primary cause in 12 of the 100 dogs in the same study. [4]
- Ear mites. Found in 7 of the 100 dogs. [4]
- Hormonal and other skin diseases. Conditions such as hypothyroidism, keratinization disorders and immune-mediated diseases can also start the problem, although hormonal causes are uncommon. [1][2]
In that study, no primary cause could be identified in about a third of dogs, and a few had more than one. [4]
Secondary causes: the infection
Once the ear canal is inflamed, yeast and bacteria that normally live there in small numbers can overgrow. In the 100-dog study, Malassezia yeast was found in 66 dogs, cocci (round bacteria) in 38 and rods (rod-shaped bacteria) in 22. [4] These infections make the ear worse, but they are usually not where the problem began.
Predisposing factors: what raises the risk
These do not cause ear disease on their own but make it more likely. [1]
- Ear shape. Compared with breeds with upright ears, breeds with floppy (pendulous) ears had 1.76 times the odds of otitis externa, and breeds with V-shaped drop ears had 1.84 times the odds. [1]
- Breed. The UK study found raised odds in 16 breed types, including the Basset Hound, Chinese Shar Pei, Labradoodle, Beagle and Golden Retriever. Chihuahuas, Border Collies, Yorkshire Terriers and Jack Russell Terriers had lower odds. [1] Spaniels have been found to have more wax glands and hair follicles lining the ear canal, and a hairy canal (as in poodles) or a large hanging ear flap (as in Basset Hounds) can stop air moving through the ear and let debris build up. [2]
- Swimming and humidity, which keep the ear canal moist. Too much ear cleaning can do the same. [1][2]
Perpetuating factors: why it keeps going
Long-term inflammation changes the ear itself. In the 100-dog study, narrowing of the ear canal (38 dogs) and a ruptured eardrum with middle ear infection (25 dogs) were the most important factors keeping the disease going. [4] This is why early, thorough treatment matters.
What your vet will do
Examine the ear canal
Your vet will look down the canal with an otoscope, a lighted magnifying instrument, to check the canal and the eardrum. Sore ears may need sedation or anesthesia so the vet can see properly. [2]
Look at the discharge under the microscope
A swab of ear discharge is examined to look for yeast, bacteria and ear mites. This tells your vet which medicine is most likely to work, and the check is repeated at recheck visits. [2]
Clean and treat
- The first thorough clean is usually done in the clinic, so the canal is clear of discharge and debris before any medicine goes in. Your vet checks the eardrum first, because some ingredients should not be used if it is torn. [2]
- Medicated ear drops or ointments are the mainstay, chosen based on what the microscope shows. Your vet may also prescribe medicine for pain and inflammation. [2]
- Your vet will look for and treat the underlying cause, such as allergies. [2]
Recheck
Rechecks are part of the treatment. At each visit your vet looks in the ear again and repeats the microscope check, and treatment carries on until no yeast or bacteria are seen. Ears that have thickened from long-term inflammation rarely go fully back to normal and usually need ongoing care. [2]
Why you should not skip the vet visit
- The eardrum needs checking. Only an otoscope exam shows whether the eardrum is intact, and several common ear product ingredients should be avoided when it is torn or has not been checked. [2] So do not put drops, cleaners or home remedies in a sore ear until your vet has looked.
- Untreated infections can spread deeper. Long-standing outer ear disease often extends into the middle ear. If the inner ear becomes involved, a dog can develop a head tilt, poor balance and flicking eye movements, and some hearing can be lost. [3]
- Chronic changes are hard to reverse. Narrowing of the canal is one of the main reasons ear disease keeps going. [2][4]
How to clean your dog’s ears safely
Ask your vet whether your dog needs routine ear cleaning, and which cleaner to use. Healthy ears often need little help, and the authors of the large UK study recommend a cautious approach that avoids overzealous ear cleaning. [1]
If your vet recommends cleaning, ask them to show you how the first time. The usual method is: [2]
- Use the ear cleaner your vet recommends. The right one depends on the type of discharge and how sore the ear is.
- Fill the canal with cleaner until it starts to run out.
- Hold the base of the ear and gently squeeze and massage it to loosen the debris.
- Let your dog shake their head, then wipe loose debris from the ear flap and the opening of the canal with a dry cotton ball, only in the parts you can clearly see. Repeat until the cotton ball comes away clean.
- Ask your vet how long to wait before putting in any medicine they prescribed.
- Do not push cotton swabs into the canal. They can pack discharge deeper and irritate the ear.
Home remedies to avoid
Skip home remedies such as vinegar mixtures. Vinegar is an acid, and acidic solutions make raw, ulcerated ear canals more painful and can make the inflammation worse. Acetic acid and alcohol are also on the list of ingredients to avoid when the eardrum may be torn. [2] Avoid putting oils, alcohol, hydrogen peroxide or other household products in your dog’s ears unless your vet tells you to.
Can ear infections be prevented?
You cannot prevent every one, but you can lower the risk:
- Treat the underlying cause. Since allergies are the most common primary cause [4], good long-term allergy management with your vet is often the most effective prevention.
- Dry the ears after swimming or bathing, especially in floppy-eared breeds. [1][2]
- Follow your vet’s cleaning plan, without overdoing it. [1]
- Check the ears weekly for redness, smell or discharge so problems are caught early.
- Check for grass seeds after walks in long grass, especially in spaniels. In the 100-dog study, grass-awn ear disease was linked with cocker spaniels and sudden-onset cases. [4]
- Go to every recheck until your vet confirms the infection has cleared. [2]
When to see your vet
Book a visit if your dog is shaking their head, scratching an ear, or has redness, smell or discharge. Go promptly if:
- Your dog is in obvious pain or will not let you touch the ear
- The ear flap suddenly swells like a pillow
- Your dog has a head tilt, loss of balance, walks in circles, or eye flicking [3]
- Your dog seems to have trouble hearing
- Signs started suddenly after a walk in long grass
Frequently asked questions
Why does my dog’s ear smell?
A bad smell is a common sign of ear infection, often from yeast or bacteria overgrowing in an inflamed ear canal. [2][4] See your vet, who can look at a swab under the microscope to find out what is growing.
Can I treat my dog’s ear infection at home?
Not safely without a vet exam. Your vet needs to check the eardrum and identify the type of infection before choosing a medicine. [2] Acidic home remedies such as vinegar mixtures can make a sore ear more painful. [2]
Which dogs get ear infections most often?
In a UK study of more than 22,000 dogs, breeds with raised odds included Basset Hounds, Chinese Shar Peis, Labradoodles, Beagles and Golden Retrievers, and dogs with floppy or V-shaped drop ears had higher odds than dogs with upright ears. [1]
Why do my dog’s ear infections keep coming back?
Usually because the primary cause, most often allergy, has not been controlled, or because long-term inflammation has narrowed the ear canal or damaged the eardrum. [4] Ask your vet about looking for the underlying cause.
Should I clean my dog’s ears with cotton swabs?
No. Cotton swabs can pack discharge deeper into the canal and irritate it. Use the cleaner your vet recommends and a dry cotton ball on the parts you can see. [2]
Are ear infections in dogs contagious?
Most are not, because they are driven by the individual dog’s allergies, ear shape or other factors. Ear mites are an exception: they can spread between pets, so your vet may treat all animals in the household if mites are found.
The bottom line
Ear infections in dogs are common, uncomfortable and often linked to allergies, with ear shape, breed and moisture raising the risk. A vet exam with an otoscope and a look at the discharge under the microscope is the quickest way to the right treatment, and finding the underlying cause is the key to stopping repeat infections.
See your vet if your dog is shaking their head, scratching an ear or has a smelly ear, and promptly if there is pain, a swollen ear flap or balance problems.
This article is for general information only and is not a substitute for professional veterinary advice, diagnosis or treatment. Always consult your veterinarian about your pet’s health. If you think your pet has a medical emergency, contact your veterinarian or an emergency animal hospital right away.
Sources
- O’Neill DG, Volk AV, Soares T, Church DB, Brodbelt DC, Pegram C. Frequency and predisposing factors for canine otitis externa in the UK: a primary veterinary care epidemiological view. Canine Medicine and Genetics. 2021;8:7. doi:10.1186/s40575-021-00106-1. https://pmc.ncbi.nlm.nih.gov/articles/PMC8422687/
- Torres SMF. Otitis Externa: Dogs and Cats. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota, 2025 (CC BY 4.0). https://open.lib.umn.edu/animaldermatology/chapter/otitis-externa-dogs-and-cats/
- Torres SMF. Otitis Media: Dogs and Cats. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota, 2025 (CC BY 4.0). https://open.lib.umn.edu/animaldermatology/chapter/otitis-media-dogs-and-cats/
- Saridomichelakis MN, Farmaki R, Leontides LS, Koutinas AF. Aetiology of canine otitis externa: a retrospective study of 100 cases. Veterinary Dermatology. 2007;18(5):341-347. https://pubmed.ncbi.nlm.nih.gov/17845622/