Ear Infections in Dogs: Signs, Causes and Treatment

Signs of an Ear Infection in Dogs

• Head shaking and scratching at the ears^7,5
• A bad or yeasty smell⁷
• Brown, black or yellow discharge, or a lot of wax^7,8
• Redness and swelling of the ear canal⁷
• Pain when the ear is touched⁷

Constant head shaking can burst a blood vessel in the ear flap and cause a swollen, fluid-filled flap (an aural hematoma). Over half of dogs with this problem also had an ear infection recorded.⁹ See swollen ear flaps in dogs.

What Causes Ear Infections in Dogs?

Vets think of ear infections in three layers: the primary cause that starts the inflammation, predisposing factors that make it more likely, and perpetuating factors that keep it going.² Bacteria and yeast are usually secondary invaders, not the root cause.^2,4

• Allergies (environmental allergies and food allergies) are the most common primary cause, especially of recurrent infections.^3,4,5 See allergies in dogs.
• Foreign bodies, especially grass seeds (awns), which often cause sudden signs.^4,5
• Ear mites, more common in puppies, causing dark, coffee-ground debris.^7,5
• Hormone disorders such as an underactive thyroid.^2,7 See thyroid disease in dogs.
• Moisture from swimming or bathing, and ear shape.^2,5

Breeds Prone to Ear Infections

In the UK study, breeds with the highest odds compared with crossbreeds were the Basset Hound, Chinese Shar Pei, Labradoodle, Beagle and Golden Retriever. The Chihuahua, Border Collie, Yorkshire Terrier and Jack Russell Terrier had the lowest.¹ Heavier dogs and dogs with drooping or V-shaped ears were also at higher risk.¹ Cocker Spaniels were overrepresented in a Greek study of 100 dogs with ear infections.⁴

Yeast vs. Bacterial Ear Infections

Yeast (Malassezia) was the most common secondary organism in one study, found in 66 of 100 dogs with otitis, followed by round bacteria (cocci) in 38 and rod-shaped bacteria in 22.⁴ Yeast infections often produce brown, waxy discharge,^8,10 while rod bacteria such as Pseudomonas can cause ulcerated, painful ears with a slimy green or pus-like discharge and a strong smell, and can be harder to treat.^2,11 You can't reliably tell them apart by looking, so a vet checks a swab under the microscope.² See yeast ear infections in dogs.

Middle and Inner Ear Infections

Infection can spread past the eardrum into the middle ear (otitis media), especially in long-standing cases. Many affected dogs still have an intact eardrum.^6,11 Signs can include a head tilt or poor balance,^5,6 or a drooping face or a smaller pupil and droopy eyelid on one side.⁶ X-rays can miss it; CT or MRI is more sensitive.¹² Middle-ear infections usually need medicine by mouth as well as ear treatment, often for several weeks.^2,12

How Vets Diagnose Ear Infections

• Otoscope exam to look down the canal, check the eardrum and look for grass seeds or growths. Sore dogs may need sedation.^7,2
• Ear cytology: a swab of discharge examined under the microscope to identify yeast, cocci or rods. White blood cells are never normal.^2,11
• Culture and sensitivity when rods are seen, the infection is chronic, or oral antibiotics are being considered.^2,7
• Tests for underlying causes, such as an allergy work-up or thyroid tests, in dogs with repeat infections.^3,7

Treatment

Most ear infections are treated with a thorough cleaning and medicated ear drops that combine an antibiotic, an antifungal and a steroid. Published cure rates for these products are often over 90%.³ Some products are given as a single long-acting dose at the clinic.^13,14 Oral antibiotics aren't needed for an outer-ear infection alone.² Acute infections usually clear in 2 to 4 weeks, with rechecks until a swab shows the infection has gone.²

See how to treat a dog ear infection for details, including how to clean your dog's ears.

Chronic and Recurring Ear Infections

An infection that returns within 3 months of clearing is considered recurrent. The most common reason is an underlying allergy that hasn't been controlled.³ Over time, chronic inflammation thickens and narrows the ear canal and can calcify it.^2,7 Most ear canal surgery is avoidable if recurrent otitis is managed well early on.³

When the canal is permanently blocked, a surgeon may recommend removing it (total ear canal ablation, or TECA). It relieves pain, but hearing on that side is usually reduced or lost (though many of these ears already hear poorly before surgery), and nerve problems are common afterward. In one study of dogs and cats, 48.9% of ears had facial nerve weakness or paralysis after surgery; in dogs it lasted more than a year in 8.3% of ears.^7,15

Preventing Ear Infections

• Treat the underlying cause, especially allergies, with your vet.³
• Gently dry the ears after swimming or bathing.⁵
• Clean only as often as needed. Healthy ears often need little cleaning, and overcleaning can irritate them.^16,17
• Finish the full course of treatment and go to recheck appointments, even if the ear looks better.^2,11
• Check ears after walks in areas with long grass and seed heads.^4,5

Frequently Asked Questions

What does a dog ear infection look like?

Red, swollen skin in the ear canal with brown, yellow or bloody discharge, often with a bad smell. Dogs shake their head and scratch.

What causes ear infections in dogs?

Most often allergies, followed by grass seeds, ear mites, moisture and hormone problems. Bacteria and yeast then take hold.

Will a dog ear infection go away on its own?

Rarely. Untreated infections tend to get worse and can spread to the middle ear or cause permanent canal damage.

Are dog ear infections an emergency?

Usually not, but see a vet promptly. Go sooner for a head tilt, loss of balance, a drooping face or severe pain.

Why does my dog keep getting ear infections?

Usually because of an underlying cause, most often allergies, that hasn't been controlled. Ask your vet about an allergy work-up.

Which dogs get ear infections most?

Basset Hounds, Shar Peis, Labradoodles, Beagles, Golden Retrievers and Cocker Spaniels, plus dogs with floppy ears.

Can a dog ear infection cause deafness?

Severe or chronic infections can reduce hearing, and surgery to remove the ear canal usually causes deafness on that side.

Are dog ear infections contagious?

Bacterial and yeast infections generally aren't. Ear mites, however, spread easily between pets.