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

Your dog has been shaking their head all morning. One ear smells off. They keep pawing at the side of their face and flinching when you touch it. You already know something is wrong — the question is how serious it is, and whether this is something that needs a vet today or can wait until next week. The short answer: ear infections in dogs don't clear on their own, and the longer they go untreated, the worse they tend to get.

Here's what's actually happening in that ear, why it keeps coming back in some dogs, and what the treatment process looks like.

What a dog ear infection actually is

The technical term for the most common type is otitis externa — an infection of the outer ear canal. Dogs have an L-shaped ear canal, which means debris, moisture, and microorganisms can get trapped in the lower horizontal part of the canal without draining the way a straighter canal might allow. When that environment stays warm, moist, and dark, it becomes ideal for yeast and bacteria to multiply.

Most dog ear infections involve yeast (Malassezia), bacteria, or both simultaneously. These organisms live on healthy skin in small numbers, but when the ear's normal environment is disrupted — by moisture, inflammation, or a shift in pH — they grow unchecked. That overgrowth causes the discharge, odor, and inflammation that produce the symptoms you're noticing.

Middle ear infections (otitis media) and inner ear infections (otitis interna) are deeper and more serious. These are less common but can develop when an outer ear infection is untreated long enough, or when infection spreads along the eustachian tube. Middle and inner ear infections typically cause more dramatic signs: head tilting, loss of balance, and in severe cases, neurological symptoms. Any dog showing those signs needs to be seen the same day.

Signs to watch for

Ear infections rarely develop without early warning. The most common signs owners notice include:

• Head shaking — repeated, often vigorous. This is the body's attempt to dislodge whatever is causing discomfort.
• Scratching at one or both ears — sometimes to the point of causing secondary wounds on the ear flap or around it.
• Bad odor — a yeasty, musty, or foul smell coming from the canal entrance, distinct from normal dog smell.
• Discharge — brown, black, or yellowish material visible at or near the opening of the ear canal.
• Redness and swelling — the skin inside the ear flap or at the canal opening looks inflamed, darker pink or red than normal.
• Pain on touch — the dog pulls away, vocalizes, or snaps when you reach toward the ear or the base of the jaw on that side.
• Head tilt — the dog carries their head tilted toward the affected ear, particularly with deeper infections.

Some dogs show only one or two of these signs. A dog who is head-shaking but otherwise acting normally is still worth calling about — catching an infection early makes treatment faster and more effective.

Why ear infections happen — and why some dogs get them constantly

Yeast and bacteria overgrow when the ear environment shifts in their favor. That's the proximate cause. But the question we're always trying to answer is: why did the environment shift? Because if you treat the infection without finding the answer to that, the infection comes back. Same ear, same cycle, 3 months later.

Allergies

This is the one most owners haven't been told about. Recurring ear infections — two or three in a year, or more — are almost never just bad luck. They're almost always driven by allergies. Environmental allergies (dust mites, grass, mold) and food allergies both cause skin inflammation throughout the body, including in the ear canal. That inflammation changes the microenvironment and makes it easy for yeast and bacteria to take hold. Treating the infection alone is like drying the floor while the faucet is still running. We see this pattern constantly, and it's underdiagnosed because the skin findings can be subtle.

Ear anatomy

Dogs with floppy ears — Cocker Spaniels, Basset Hounds, Golden Retrievers — have ears that lay flat against the head and restrict airflow into the canal. Warmth and moisture build up, creating better conditions for infection. Dogs with narrow ear canals or a lot of hair growing in the canal are also at higher risk. These are structural predispositions that can be managed but not changed.

Moisture

Water in the ear canal from baths, swimming, or rain is a direct trigger. The moisture raises humidity inside the canal, and combined with warmth, creates the conditions yeast thrive in. Dogs who swim regularly and get ear infections should have their ears dried after every water exposure and may benefit from a veterinary-recommended ear drying solution used routinely.

Foreign material and ear mites

Grass awns, plant material, and debris can lodge in the ear canal and cause intense irritation and secondary infection. Ear mites are more common in puppies and outdoor cats, but dogs can get them — they cause a distinctive dark, coffee-ground-like discharge and intense itching. A vet exam distinguishes mites from bacterial or yeast infections because treatment differs significantly.

Hormonal conditions

Hypothyroidism (underactive thyroid) affects skin quality throughout the body, including in the ear canal, and predisposes dogs to recurring ear infections. Dogs with recurring skin problems and recurring ear infections should have thyroid function evaluated if it hasn't been already.

What happens at the vet

The first thing we do is look into the canal with an otoscope. Not just peek — actually assess how far the infection has gone and whether the eardrum is intact. This isn't a formality. If the eardrum is ruptured, certain topical ear medications that are completely safe in an intact ear can cause serious damage in the middle ear. The treatment literally changes based on what we see.

We also run a cytology — a quick in-house microscope look at the discharge from the ear. This tells us whether it's yeast, bacteria, or both, and roughly in what proportion. It matters because they don't respond to the same medications. A mostly-yeast infection treated with a pure antibacterial ointment won't clear. Same in reverse. Most practices can turn this around during the appointment, which means treatment starts that day.

For straightforward outer ear infections, treatment typically involves:

• A thorough professional ear flush to remove built-up debris from the canal
• A topical medicated ointment applied into the canal — usually a combination product covering yeast and bacteria
• Instructions for at-home cleaning and follow-up applications
• A recheck appointment in 2–3 weeks to confirm the infection has cleared

More involved cases — infections that have been present for weeks, infections with severe swelling that has narrowed the canal, or dogs with suspected middle ear involvement — may require oral antibiotics, anti-inflammatory medication, or referral for imaging. The goal of the recheck isn't just to see if the dog seems better; it's to confirm the infection is actually gone with a follow-up cytology, because a partially treated infection is still an infection.

At-home ear cleaning — what helps and what doesn't

Routine ear cleaning between vet visits can help maintain ear health in dogs who are prone to buildup. The key is using a veterinary-formulated ear cleaner — not hydrogen peroxide, not rubbing alcohol, not plain water, and not cotton swabs inserted into the canal. The right cleaner helps break up wax and debris and acidifies the canal environment to make it less hospitable to yeast and bacteria.

The technique matters. Squeeze an appropriate amount of cleaner into the ear canal, massage the base of the ear gently for 20–30 seconds to work it into the horizontal part of the canal, then let the dog shake their head. Wipe the visible part of the ear flap and canal entrance with a cotton ball or soft gauze. Never push anything down into the canal — this compacts debris instead of removing it and risks damaging the eardrum.

How often to clean depends on the individual dog. A dog who has never had ear problems and has upright ears may not need routine cleaning at all. A dog who gets infections every summer, swims frequently, or has floppy ears may need cleaning weekly during high-risk periods. Ask your vet what schedule makes sense for your specific dog rather than following a generic recommendation.

When it can't wait

Most ear infections, while uncomfortable, are not emergencies. But a few situations mean same-day attention:

• Your dog is in obvious severe pain — crying, unable to settle, won't let you near their head
• The ear is producing bleeding or blood-tinged discharge
• The dog has developed a head tilt, is walking in circles, or has lost balance
• A large, fluid-filled swelling has appeared on the ear flap (this is an aural hematoma — blood pooling from aggressive head shaking — and requires drainage)
• The dog cannot open or close their mouth normally on the side of the affected ear

If you're in the Alhambra, South Pasadena, San Marino, or surrounding area and your dog is showing any of these signs, contact us to get them seen the same day. For a dog who's uncomfortable but stable, an appointment within 48 hours is appropriate — don't wait weeks hoping it resolves.

You can find information about what an ear exam and treatment typically involves on our services page, or check our pricing if you want to understand costs before coming in.

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