Dog ear infections: signs, causes, treatment and prevention

Your dog keeps shaking its head, scratching one ear with a back paw, and when you lean in, there's a sour smell that wasn't there last week. Dog ear infections are one of the most common reasons for a vet visit, and when they're treated properly, most clear up within a few weeks. The catch is that many come back, because the infection gets treated but the reason it started doesn't.

This guide explains how to recognize an ear infection, what different kinds of discharge suggest, why ears get infected, which signs make it urgent, what your vet will do and how to keep it from returning.

What an ear infection is and the different types

Vets call ear inflammation otitis. A dog's ear canal is long and L-shaped, which makes it harder for wax and moisture to work their way out; we cover the anatomy in how to clean your dog's ears. Depending on which part is affected, there are three types:

The vast majority are outer ear infections. Middle and inner ear infections usually develop when an outer ear problem becomes chronic or isn't treated in time.

Signs of an ear infection in dogs

• Frequent head shaking or scratching at the ears.
• A bad smell from the ear (sour, sweet, yeasty or rotten).
• Brown, black, yellow or greenish discharge.
• Red, hot or thickened skin in the canal or on the ear flap.
• Pain: pulling away or yelping when you touch the ear or head, or reluctance to chew.
• Tilting the head toward the sore side.
• An ear flap that swells up like a soft pillow (an aural hematoma, caused by violent shaking).
• Reduced hearing in advanced cases.

Ear infections hurt more than many owners realize, and some dogs only show it in subtle ways: grumpiness, eating less or avoiding pats on the head. If you're not sure how to read your dog, review the signs your dog is in pain.

What the discharge can tell you

Treat this as a rough guide only: how it looks isn't enough to choose a treatment. Only ear cytology (a swab examined under the microscope) shows which organisms are actually there.

What causes ear infections in dogs

Vets think about ear infections as layers of factors that stack up. Understanding them explains why some infections never seem to fully go away.

• Primary causes start the problem. Allergies (environmental and food) are the most common. Others include foreign bodies like foxtails, ear mites, hormonal disorders such as hypothyroidism and, less often, autoimmune disease or polyps.
• Predisposing factors make infection more likely: floppy ears, hairy ear canals, narrow canals, moisture from baths or swimming and over-cleaning or using cotton swabs.
• Secondary causes make inflammation worse: bacteria and yeast that normally live in the ear in small numbers and overgrow once conditions change.
• Perpetuating factors keep it going: chronic changes like thickened canal skin, a narrowed or calcified canal, or a middle ear infection.

That's why an ear infection that returns every few months almost always has an unsolved primary cause, very often an allergy. If your dog also scratches its paws, face or belly, read our guide to why your dog is so itchy.

Breeds at higher risk

Cocker spaniels (one of the most predisposed breeds), basset hounds, beagles, Labrador and golden retrievers, poodles, Shar-Peis, French bulldogs and West Highland white terriers are more prone, whether because of ear shape, hair in the canal or a tendency toward allergies.

When is a dog ear infection an emergency?

Most outer ear infections aren't emergencies, but your vet should see them within a day or two. The pain is real, and the sooner treatment starts, the easier it is to keep the problem from becoming chronic.

What to do at home until your vet appointment

1. Don't clean the ear on the day of the visit. Your vet needs to see the discharge and take a sample for cytology.
2. Don't put anything in the ear: no leftover drops from a previous infection, no human ear drops, hydrogen peroxide, rubbing alcohol, vinegar or oils. If the eardrum is damaged, some products can harm the middle and inner ear.
3. Don't try to remove a foxtail or go in with a cotton swab: you'll push it toward the eardrum. Learn more about foxtails in dogs.
4. Prevent self-injury. A cone helps if your dog is scratching hard enough to break the skin.
5. Write down what your vet will ask: when it started, one ear or both, whether your dog swims or gets bathed often, whether it itches anywhere else and what treatments it's had before.

How vets diagnose and treat ear infections

Diagnosis usually includes:

• Otoscopic exam: a look down the canal at the eardrum. If the ear is very painful or packed with debris, your dog may need sedation.
• Ear cytology: a sample of the discharge under the microscope to check for bacteria (and what shape they are), yeast or inflammatory cells. It's the key test for choosing treatment, and it's repeated at the recheck.
• Culture and sensitivity testing for chronic or recurring infections, or when cytology shows bacteria that are often resistant.
• Imaging (such as a CT scan) if a middle ear infection is suspected.

In general terms, treatment combines a thorough in-clinic ear flush (sometimes under sedation), ear medication targeted to what was found and, depending on the case, oral treatment for inflammation or infection. Some clinics can apply long-acting ear medications so you don't have to give drops every day at home.

A straightforward outer ear infection usually improves within a few days, and treatment typically lasts one to two weeks, with a recheck before stopping to confirm it's truly gone. Stopping as soon as your dog "seems fine" is one of the most common reasons for a relapse. Chronic infections can take weeks or months, and when the canal is permanently narrowed or calcified, surgery is the last resort.

Recurring ear infections: how to break the cycle

If your dog gets three or four ear infections a year, the goal is no longer just to clear the next one but to understand why they keep coming back. That typically means:

• Finding the primary cause, often environmental allergies or a food allergy investigated with an elimination diet of at least 8 weeks.
• Setting up a maintenance plan with a specific ear cleaner and schedule from your vet.
• Getting ears checked at the first sign (odor, head shaking) instead of waiting for the infection to take hold.
• Managing moisture in dogs that swim.

How to prevent ear infections in dogs

• Check your dog's ears weekly: lift the flap, look with good light and sniff. A new smell is often the first warning.
• Clean only when needed, using a veterinary ear cleaner; over-cleaning irritates the canal.
• Dry the ears well after baths and swimming, especially in floppy-eared breeds. Our guide on how often to bathe a dog explains how to wash the head without soaking the ears.
• Check ears after hikes in late spring and summer, peak foxtail season in much of the West.
• Keep allergies under control and always finish prescribed treatments.
• Have the hair around the ear opening trimmed in long-coated breeds so the ear can breathe.

Frequently asked questions

Are dog ear infections contagious?

The infection itself doesn't spread from dog to dog, because it mostly depends on each dog's own risk factors, like allergies or ear shape. The exception is ear mites, which pass easily between dogs, cats and ferrets in the same home. If your vet confirms mites, plan on treating every pet in the household at the same time.

Can a dog ear infection go away on its own?

Rarely. Very mild irritation may settle if the trigger disappears, but an infected ear usually gets worse without treatment and can become chronic or spread to the middle ear. It's also painful. If your dog has been shaking its head or has had a smelly ear for more than a day or two, it's worth a vet visit.

Can an ear infection make my dog deaf?

During a bad infection, many dogs hear less because the canal is swollen and full of debris, and that usually improves once it heals. The risk of permanent hearing loss is mainly linked to long-standing, poorly controlled infections or those involving the middle and inner ear. Treating promptly and finishing the full course is the best protection.

Why does my dog only have an infection in one ear?

When just one ear is affected, vets first look for something local: a foxtail or other foreign body, a polyp or a growth in the canal. Allergy-related ear infections, on the other hand, usually affect both ears, even if one looks worse. That's why a full otoscopic exam of the entire canal matters.

How much does it cost to treat a dog ear infection?

It depends on whether it's a first episode or a chronic problem. An exam, cytology and medication for a simple outer ear infection is usually a moderate expense, while chronic cases that need cultures, sedation, imaging or surgery can cost much more. Treating it thoroughly the first time is usually the cheapest route.

Sources

• Merck Veterinary Manual: otitis externa, otitis media and otitis interna in dogs.
• American College of Veterinary Dermatology (ACVD): pet owner information on ear infections.
• VCA Animal Hospitals: ear infections in dogs.
• American Kennel Club (AKC): symptoms and prevention of ear infections.