The Canine Ledger

Ear Infections: Why They Keep Coming Back

A recurring ear infection is almost always a sign of something else, often allergy. Why drops alone don't stop it, and the signs that can't wait.

Written by thecanineledger

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Phone your vet today if your dog with ear trouble develops a head tilt, loses their balance, walks in circles, has eyes flicking from side to side, or can’t blink or move one side of their face. These can mean the infection has reached the middle or inner ear.

A veterinary dermatologist reviewing what is known about recurring ear infections in dogs put the central point in one line: “clinicians must appreciate that all recurrent ear infections in dogs are secondary” (Nuttall, J Am Vet Med Assoc 2023).

Secondary means something else started it. The infection is real and needs treating, but it is the result, not the cause. While a course of ear drops will usually clear a flare, if nothing is done about what set it off, the same ear tends to flare again, and each round does a little more damage.

The same review is blunt about where that ends: “Eventually, the changes become irreversible and require a total ear canal ablation/lateral bulla osteotomy or ablative laser surgery.” That is surgery to remove the ear canal. It then adds the hopeful part: “Most ear canal surgery is avoidable if recurrent otitis is properly managed at an earlier stage.”

This page explains what “properly managed” means, and what you can do to help.

1. How common this is

Very. A study of UK veterinary records from 2016, covering a random sample of 22,333 dogs, found that 7.3% were treated for an outer-ear infection or inflammation, called otitis externa, in one year (O’Neill et al., Canine Med Genet 2021). The Merck Veterinary Manual calls it “one of the most common reasons for dogs and cats (especially dogs) to be brought to the veterinarian” (Merck, Otitis Externa in Animals).

Some dogs are far more likely to get it. In the UK study, Basset Hounds had nearly six times the odds of crossbred dogs, and Chinese Shar Peis, Labradoodles, Beagles and Golden Retrievers were also at higher risk. Dogs with hanging ears had 1.76 times the odds of dogs with upright ears. Chihuahuas, Border Collies, Yorkshire Terriers and Jack Russell Terriers were less likely to be affected. These are UK figures.

2. Why ear infections keep coming back

Vets think about ear disease in four layers. Merck’s chapter and Nuttall’s review both use them.

Primary causes start the problem in a healthy ear. Merck lists them, and allergy comes first: “allergy (adverse food reaction, atopic dermatitis, allergic contact dermatitis).” Others include ear mites and other parasites, grass seeds and other foreign bodies, hormone diseases such as an underactive thyroid, and some immune conditions.

Secondary causes are the infections, by bacteria or yeasts, that take hold once the ear is inflamed.

Predisposing factors make it more likely. Merck lists ear shape (“pendulous pinna, stenotic canals, hairy concave pinna, excessive hair in canals”), moisture from swimming or the environment, and anything blocking the canal.

Perpetuating factors keep it going. These are changes the inflammation itself causes, such as a narrowed, thickened canal or a damaged eardrum. They are why a long-standing ear gets harder to treat.

Nuttall’s review says that a good long-term result needs every layer dealt with: “the primary condition must be diagnosed and managed, the secondary infection treated, predisposing risks identified and corrected, and the perpetuating factors reversed.”

Merck’s guide for owners says the same in plainer words: “Unless every cause is treated, the condition often returns” (Merck, Ear Infections and Otitis Externa in Dogs).

For many dogs, the primary cause is allergy. If your dog’s ears keep flaring and they also lick their paws, scratch, or get red skin, tell your vet. → The Itchy Dog: Allergies, Atopic Dermatitis, and What Actually Helps

Our note: We say allergy is the main cause “for many dogs” with repeat ear infections. We didn’t find a figure for how often.

3. When the middle ear is involved

The eardrum separates the outer ear canal from the middle ear. Infection can get through it. Merck’s owner guide notes that “Otitis media is found in over half of dogs with recurrent external ear inflammation” (Merck, Otitis Media and Interna in Dogs). Otitis media is a middle-ear infection.

This matters for two reasons. A middle-ear infection is one reason an outer-ear infection keeps returning, and it usually needs longer treatment. It can also spread to the inner ear, which controls balance. Merck says an inner-ear infection “typically results in a head tilt toward the affected side and can cause severe coordination problems, difficulty rising and walking, and uncontrollable eye movements.” Because the nerves to the face run through the middle ear, a dog may also be unable to move their face, eyes or eyelids on one side.

Those are the signs in the box at the top of this page. Don’t wait to see if they pass.

Our note: A head tilt, loss of balance, abnormal eye movements or facial paralysis can also come from other conditions, including emergencies. If you see them, call your vet straight away.

4. Treating a flare

Merck’s owner guide describes what a vet usually does. They look down the canal with an otoscope, sometimes under sedation if the ear is painful, and often take a swab to look at under the microscope. That swab shows whether bacteria, yeasts or mites are present, which decides the treatment.

The ear is usually cleaned before drops go in, because “Topical medications (applied to the skin) can be inactivated by discharge or wax.” Most ear drops combine an antibiotic, an antifungal and an anti-inflammatory, and the vet chooses the product.

Finish the course, and go back for the recheck. Merck is clear that “Treatment must continue until the infection is fully cleared,” and that dogs with bacterial or yeast infections “usually need repeated veterinary checkups until no infection shows, often 2–4 weeks.” An ear that looks better at home can still be infected. Stopping early is one route to the next flare.

Don’t use home remedies. Merck warns owners to “Avoid irritating home remedies (like vinegar mixtures) because they can worsen swelling and secretions and increase infection risk,” and adds that “Even products normally safe in healthy ears can irritate inflamed ears.”

Don’t use leftover ear drops from an earlier infection or another dog. The vet needs to see the ear first, partly to check whether the eardrum is intact.

Our note: We haven’t read a source on which ear products are unsafe with a ruptured eardrum. Don’t use leftover drops.

5. Keeping the ears well

Nuttall’s review describes treatment of recurrent ear disease in two phases: “induction to get the ears in remission and then long-term maintenance therapy to prevent relapses.” What maintenance involves depends on the dog. It may include regular cleaning, treating the underlying allergy, and sometimes medication between flares.

Clean only if your vet says to, and only the way they show you. Merck’s owner guide gives a method, but it starts with the advice to follow your vet’s instructions. It also warns against cotton buds: “Don’t use anything that pushes debris deeper in the canal. Don’t use cotton swabs.”

Check the ears. Merck suggests regular checks for changes in temperature, colour or moisture, and “Prompt veterinary attention is needed when changes appear.” Catching a flare early is easier than treating an established one.

Keep the ears dry. Merck advises keeping water out of the ears when bathing, and asking your vet about drying products for dogs who swim a lot.

Ask before plucking ear hair. Merck says that in some cases trimming or plucking hair near the canal improves airflow, “but consult your vet before removing hair.” It isn’t right for every dog.

Our note: Merck suggests regular cleaning mainly for dogs who often get ear infections.

6. What to ask your vet

If your dog has had three or four ear infections, it’s reasonable to ask:

  • What do you think is starting them? Is it allergy, ear shape, swimming, something else?
  • Is the middle ear involved?
  • What does maintenance look like once this flare is cleared?
  • Would seeing a veterinary dermatologist help?

None of these questions criticise the treatment so far. Recurring ear disease is hard, and Nuttall’s review says that handling it well “requires a different mindset and approach to these cases.”

Our note: “Three or four” infections before asking about a referral is our number.

7. What we could not verify

Commonly saidWhat we found
“Ear infections mean the ears are dirty”Not the main story. Merck lists allergy first among the primary causes. Dirt and wax are more often a result.
“Vinegar or cider vinegar cures ear infections”Merck advises against it. It can “worsen swelling and secretions and increase infection risk.”
“Floppy ears cause ear infections”A risk factor, not a cause. Hanging ears had 1.76 times the odds in a UK study, but many floppy-eared dogs never have one.
“Always pluck the hair from a dog’s ears”Not for every dog. Merck: “consult your vet before removing hair.”
“Once the ear looks better, you can stop the drops”No. Merck: treatment must continue until the infection is fully cleared, often with rechecks over 2–4 weeks.
How often allergy is behind recurrent ear diseaseNo figure read.

Sources

Always confirm with your vet before acting on anything on this page.