Dog Ear Infections: Signs, Causes and When to See a Vet

Your dog keeps shaking their head. You lift the ear flap and catch a sour, musty smell. The skin looks red and there's brown gunk inside. It's an ear infection, or it looks like one.

Ear infections are one of the most common reasons dogs see a vet. They're also easy to get wrong. This guide helps you read the signs, understand what's behind them and know what to expect from treatment.

What is an ear infection in dogs?

The medical name is otitis externa. It means inflammation of the lining of the outer ear canal. Your dog's canal isn't a straight tube like ours. It drops down the side of the head, then turns sharply toward the eardrum. That bend is warm, dark and prone to trapping moisture and wax. It's like a boot that never fully dries.

When the lining gets irritated, the skin's normal bacteria and yeast multiply. That overgrowth is what most people call the infection. It can affect one ear or both.

Signs of an ear infection in dogs

Most dogs show several of these:

• Shaking the head or tilting it to one side
• Scratching at the ear with a back paw
• Red, swollen or hot-feeling skin inside the ear
• A bad smell
• Brown, yellow or black discharge
• Scaly, crusty or thickened skin
• Pain when the ear is touched
• Rubbing the ear on furniture or the floor

Dogs with long-standing infections may have thickened, crusty ears with narrowed canals. That change is hard to reverse, which is a good reason to act early.

What does a dog ear infection look like?

Lift the flap and look at the skin. Healthy ears are pale pink and clean. An infected ear is often red or dark pink, with a layer of discharge coating the folds. The canal opening may look puffy or narrow.

Don't poke inside. If you can see the problem from the outside, that's enough to book a visit.

Brown discharge: yeast or bacteria?

The color and smell of the discharge give useful hints. They aren't a diagnosis, but they help you describe the problem to your vet.

Yeast infections

Yeast thrives in warm, damp ears. The discharge is often dark brown and greasy, with a musty smell like old bread. Dogs with allergies and dogs that swim often get yeast infections a lot.

Bacterial infections

Bacteria usually produce a wetter, lighter discharge that can look yellow, and the smell is sour or rotten. These ears are often more painful. Severe bacterial infections can damage the canal lining and may reach the middle ear.

Mixed infections

Many ears have both yeast and bacteria. A vet can see which organisms are present by looking at a sample under a microscope. That's why guessing at home usually fails.

What causes dog ear infections?

Here's the key point: the infection is usually secondary. Something else made the ear a good place for yeast and bacteria to grow. The Merck Veterinary Manual lists parasites, foreign objects, allergies, bacterial and yeast infections and middle ear problems as causes. It also says that untreated underlying causes typically lead to recurrence.

Allergies

Allergies are the big one. VCA Animal Hospitals notes allergies are involved in roughly 43 percent of ear infection cases, and that 65 to 80 percent of dogs with food allergies develop ear problems. Environmental allergies to pollen or dust mites also inflame the canal. The ear is just one place where the allergy shows up. Itchy paws, belly rashes and red eyes often come with it. Our guide to red eyes in dogs covers the eye side.

Moisture and ear shape

Swimming, baths and humid weather leave water in the canal. Heavy, floppy ears hold in heat and damp. VCA lists Cocker Spaniels, Miniature Poodles and Old English Sheepdogs as particularly prone, though any breed can be affected. Breeds with narrow canals, like Bulldogs and French Bulldogs, or hairy canals, like many doodles, can also struggle, since wax and moisture get trapped more easily.

Foreign objects and parasites

A grass seed in the canal causes sudden, sharp discomfort, usually in one ear. Ear mites cause intense itching and a coffee-ground discharge. They're easy to confuse with infection, so read our guide to ear mites in dogs if the discharge is dark and crumbly.

Hormonal problems

Hormonal diseases such as hypothyroidism can also contribute, according to VCA. If your dog has repeat infections and other changes like weight gain or a dull coat, mention that to your vet.

How vets diagnose ear infections

Your vet will look down the canal with an otoscope. They check the eardrum and the skin, then take a sample of the discharge to look at under a microscope. In stubborn cases they may send a culture to find the right antibiotic. For chronic or one-sided infections, allergy testing, X-rays or other scans may help find the cause.

This matters because the eardrum may be damaged. Some ear medicines aren't safe if it is. The vet can only know that by looking.

Treatment for dog ear infections

Treatment has three parts: clean the ear, treat the infection and manage the cause.

Cleaning and medication

Vets usually clean and dry the ear, then prescribe medicated drops or ointment. The medicine is chosen to match what they found: an antibiotic for bacteria, an antifungal for yeast. Severe cases may also need an antibiotic by mouth plus anti-inflammatories to reduce swelling and discharge.

How long does it take?

Most cases settle in about two to four weeks, according to Merck. Chronic ear problems can take months or need lifelong management. Finish the whole course even if the ear looks better. Stopping early is a common reason for relapse.

Surgery

Severe chronic cases that no longer respond to medicine may need surgery. VCA mentions lateral ear resection and total ear canal ablation. These are last-resort options, usually after the canal has become permanently narrowed.

Can you treat it at home?

You can help, but you can't replace the vet. Never use leftover drops from a previous infection. They may be the wrong kind, and they're unsafe if the eardrum is damaged. Home recipes with vinegar, alcohol or peroxide sting inflamed skin.

What you can do is keep the ears clean and dry between treatments. Our guide on how to clean your dog's ears walks through the method vets recommend. Don't clean a painful, red or smelly ear before it's been seen, since cleaning can hurt and push debris deeper.

Chronic and recurring ear infections

If your dog has three or four infections a year, the problem isn't bad luck. Repeated infections thicken the ear lining. The canal narrows, wax builds up, and the next infection takes hold even faster. VCA describes chronic ears as crusty and thickened, with narrowed canals.

A chronic ear needs a plan, not another round of drops. Your vet may suggest:

• A diet trial to check for food allergy, which usually lasts several weeks and needs strict feeding
• Allergy testing or medication for environmental allergies
• A thyroid check if other signs fit
• A routine cleaning schedule between flare-ups
• Imaging if one ear keeps failing treatment

It's a lot, but it works better than treating each flare-up as a fresh surprise.

Complications of ear infections

Aural hematoma

Violent head shaking can burst small blood vessels in the ear flap. Blood pools between the skin and cartilage, and the flap puffs up like a pillow. It needs a vet. The infection or mites behind the shaking need treating too, otherwise it can happen again.

Middle and inner ear infection

When an outer ear infection goes unchecked, it can spread inward. Signs include a head tilt, loss of balance, circling, flickering eyes and sometimes hearing loss. These dogs need prompt veterinary care.

Ear infection vs other ear problems

An ear infection isn't the only reason for a dirty, itchy ear. Mites, allergies without infection, foreign objects and even heavy wax can look alike. Dark, dry, crumbly debris and itching in several pets points toward mites. A smell, redness and wet discharge points toward infection. If you can't tell, that's normal. A vet can sort it out with one look and one swab.

What to bring to the vet visit

A little preparation makes the appointment more useful. Note when the head shaking began, whether one ear or both are affected, and what the discharge looks like. Take a photo if you can. Mention any swimming, new foods, itchy paws or past ear problems.

If your dog has had infections before, bring the names of the medicines used and how well they worked. That history can save a lot of guesswork.

How to prevent ear infections

• Check ears weekly. Look at the color and give a quick sniff.
• Dry the ears after swimming and baths.
• Clean only when your vet suggests it. Over-cleaning irritates the canal.
• Manage allergies. This is often the most important step.
• Ask your vet whether hair in the canal should be trimmed for your dog's breed.
• Treat every infection early, before the canal thickens.

When to see a vet

Book a visit if your dog has head shaking, a bad smell, discharge or a red ear. Don't wait for it to clear by itself. Ear infections hurt, and delay can lead to deeper trouble.

Go the same day if you see a head tilt, loss of balance, flickering eyes, severe pain, a hot swollen ear or a puffy ear flap. A tilt or wobble can mean the infection has reached the middle or inner ear. A puffy flap is often an aural hematoma, a pocket of blood that forms after hard shaking.

Most ear infections respond well to the right treatment, and finding the underlying cause makes the best long-term difference. For more help, visit our ears and eyes section.