Ear Infections in Dogs: Causes, Signs and Treatment

A closer look at ear infections in dogs

Ear infections are one of the most common reasons dogs see a vet. Almost all of them start in the outer ear canal, the L-shaped tube that runs down from the ear flap to the eardrum. Vets call inflammation of this canal otitis externa. When the infection spreads past the eardrum it becomes otitis media (middle ear), and in rare, serious cases otitis interna (inner ear), which can affect balance and hearing.

A dog’s ear canal is long and bends sharply, which makes it good at trapping warmth, moisture and debris. That is the environment yeast and bacteria like. Both live on healthy skin in small numbers. An infection happens when something changes the ear so they can overgrow.

That “something” matters more than the germ. Vets think of ear infections in three layers: a primary cause that starts the inflammation (most often allergy), predisposing factors that make a dog more likely to have trouble (ear shape, swimming), and perpetuating factors that keep it going once it has started (thickened canal skin, resistant bacteria, a damaged eardrum). Treating only the infection, without the primary cause, is the main reason infections keep coming back.

Risk factors

Any dog can get an ear infection, but some are far more likely to:

• Dogs with allergies. Environmental allergies (atopic dermatitis) and food allergies inflame the skin lining the ear. In many allergic dogs, ear infections are the first or only sign.
• Floppy or hairy ears. Cocker Spaniels, Basset Hounds, Golden and Labrador Retrievers, Poodles and Doodles have ears that trap warmth and moisture. Cocker Spaniels are especially prone to severe, chronic disease.
• Narrow ear canals. Shar Peis, Bulldogs and some other breeds have naturally narrow canals that clog easily.
• Swimmers and frequently bathed dogs. Water left in the canal softens the skin and feeds yeast and bacteria.
• Dogs with hormone conditions. Hypothyroidism and Cushing’s disease change the skin and make infections more likely.
• Warm, humid climates. In places like the Texas Gulf Coast, ear problems peak in the humid months and in allergy season.

Causes

Primary causes (what starts it)

• Allergies: the most common cause by far. Both environmental allergies (pollens, dust mites, moulds) and adverse food reactions inflame the ear canal.
• Ear mites (Otodectes cynotis): more common in puppies and in homes with cats. They cause intense itching and a dark, crumbly discharge.
• Foreign bodies: grass awns and seeds work their way down the canal, usually causing a sudden, one-sided infection after a walk or run in long grass.
• Hormone and skin disorders: hypothyroidism, Cushing’s disease and keratinisation disorders that change how the skin produces wax and oil.
• Growths: polyps and tumours in the canal, more often in older dogs, can block it and cause infection on one side.

The infection itself

• Yeast, usually Malassezia pachydermatis: often a brown, waxy, greasy discharge with a musty, sweet or “cheesy” smell.
• Bacteria, most often Staphylococcus pseudintermedius, Pseudomonas, Proteus and Streptococcus: often a yellow or green, wet discharge and a stronger smell. Pseudomonas infections can be painful, ulcerated and resistant to common antibiotics.

Many dogs have both yeast and bacteria at once, which is one reason your vet looks at a sample before choosing a medicine.

Signs of an ear infection

• Shaking the head or holding one ear lower than the other
• Scratching or rubbing the ear on furniture or the floor
• Redness and swelling inside the ear flap or at the opening of the canal
• Brown, yellow, green or bloody discharge
• A bad smell from the ear
• Pain: pulling away or yelping when the ear or head is touched, reluctance to chew
• Crusts or scabs on the ear flap from scratching
• In long-standing cases: thickened, hardened ear canals that look narrowed

Signs that the infection may have reached the middle or inner ear (see the emergency box below) include a head tilt, loss of balance, flicking eye movements, drooping on one side of the face, and hearing loss.

Repeated head shaking can also burst a blood vessel in the ear flap, causing an aural haematoma: a soft, puffy, fluid-filled swelling of the flap. It needs a vet’s attention, and the ear infection behind it needs treating too.

How vets diagnose ear infections

Your vet will usually:

1. Ask about the history: when it started, one ear or both, whether it has happened before, diet, itching elsewhere, swimming, and any treatment you have already tried.
2. Look into both ears with an otoscope to see the canal and, where possible, the eardrum. Painful ears may need sedation before a proper look.
3. Do ear cytology: a swab of the discharge is stained and examined under the microscope. This shows whether yeast, bacteria (and which shape), mites or inflammatory cells are present, and it is quick enough to do during the visit.
4. Send a culture and sensitivity test in chronic or severe cases, or when rod-shaped bacteria are seen, to find out exactly which bacteria are present and which antibiotics will work.
5. Look for the primary cause: skin checks, a diet trial for food allergy, blood tests for hormone conditions, and sometimes video otoscopy, CT or MRI when a growth or middle-ear disease is suspected.

Treatment

Cleaning

Discharge and debris shield germs from medication, so most treatment starts with a thorough clean. Your vet may clean the ears in the clinic, sometimes under sedation for painful or deeply packed ears, and show you how to clean at home with an ear cleaner suited to your dog’s infection and eardrum.

Medication in the ear

Most outer-ear infections are treated with drops or ointment containing a combination of an antifungal, an antibiotic and an anti-inflammatory steroid. Some newer products are applied once or twice in the clinic and stay in the ear for a week or more, which helps dogs that are hard to medicate at home.

Medication by mouth

Oral steroids or other anti-inflammatories may be used for a short time to bring down severe swelling so ear medication can reach the canal. Oral antibiotics or antifungals are used for middle-ear infections or when the canal is too swollen to treat from the inside. Pain relief is often needed in the first days.

Treating the cause

This is what stops the cycle: allergy management (diet trials, anti-itch medicines, immunotherapy), mite treatment for every pet in the home, removing a foreign body, or treating a hormone condition. For dogs with allergies, your vet may suggest a regular maintenance cleaning routine and a plan to start treatment at the first sign of a flare.

Surgery

When years of infection have permanently narrowed or calcified the canal, and medical treatment can no longer reach it, surgery such as a total ear canal ablation may be recommended. It is a major operation, done by an experienced or specialist surgeon, and is reserved for end-stage ears.

Recovery and outlook

Most first-time outer-ear infections improve within a few days of starting treatment and clear within one to three weeks. Your vet will usually want a recheck before you stop treatment, and often a repeat cytology, because ears can look better while infection is still present. Stopping too early is a common reason for relapses and resistant infections.

Middle-ear infections take longer, often four to six weeks or more. Dogs with balance problems from inner-ear disease usually improve gradually over weeks, though a slight head tilt can remain.

For dogs with allergies, the realistic goal is control rather than cure: fewer, milder flares caught early.

Prevention

• Control allergies. If your dog has repeated ear infections, ask your vet about an allergy work-up. It is the single most effective step.
• Dry the ears after swimming and bathing. Your vet may recommend a drying ear cleaner after water exposure.
• Clean only as often as your vet suggests. Healthy ears clean themselves; over-cleaning can irritate them. Dogs prone to infection often benefit from a routine maintenance clean.
• Do not pluck ear hair unless your vet advises it: it can inflame the canal.
• Check ears weekly, especially in floppy-eared breeds: look for redness, discharge or smell, and catch problems early.
• Check after walks in long grass during seed season, and see a vet promptly if your dog suddenly starts shaking its head.

Ear infections by breed and age

Puppies with itchy, dirty ears are more likely to have ear mites than older dogs, especially if they came from a shelter or live with cats. Mites are easy to treat, but every pet in the home needs treating at the same time.

Young adult dogs with repeated ear infections, particularly if they also lick their paws or rub their face, very often have atopic dermatitis or a food allergy. Ear infections may be the first sign, years before itchy skin is obvious.

Older dogs with a new infection in one ear only should be checked for a growth or polyp in the canal, and for hormone conditions such as hypothyroidism.

Spaniels, especially Cocker Spaniels, are prone to severe, long-standing disease in which the canal walls thicken and calcify. Early, thorough treatment and allergy control matter even more in these breeds.

How much treatment costs

Costs vary a lot between clinics and cities, and with how severe the infection is. As a rough guide to what is involved:

Situation	What it usually involves
First, mild infection	Exam, ear cytology, a clean, and a course of ear drops or a long-acting in-clinic treatment, plus a recheck.
Painful or very dirty ears	The above, plus sedation for a deep clean and pain relief.
Repeated or resistant infection	Culture and sensitivity testing, longer treatment, and an allergy work-up or diet trial.
Middle-ear or end-stage disease	Imaging (CT), deep flushing under anaesthesia, weeks of medication, or surgery.

Ask the clinic for an estimate before treatment. Several Houston clinics publish their exam fees, which you can see on their HeiBob listings, and pet insurance taken out before problems start usually covers ear infections.

Questions to ask your vet

• What did the ear cytology show: yeast, bacteria, or both?
• Is the eardrum intact? Which cleaner is safe to use?
• How often should I medicate, for how long, and how much goes in each ear?
• When should we recheck, and what would make you want to see the ear sooner?
• What do you think is causing it? Should we look into allergies?
• Is there a long-acting treatment we can do here if medicating at home is hard?

Giving ear medication at home

Many owners find this the hardest part. A few things help:

• Clean first (if your vet has told you to), then wait 10 to 15 minutes before putting medication in.
• Warm the bottle in your hand: cold drops are unpleasant.
• Lift the ear flap, put the drops in, then massage the base of the ear so the medication runs down the canal.
• Pair every treatment with something your dog loves, and keep sessions short and calm.
• If your dog becomes too sore or upset to medicate, tell your vet rather than skipping doses. Long-acting in-clinic options and pain relief can make a big difference.