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This guide helps you understand what is going on; it does not replace a veterinary exam. A painful ear has to be looked at, not guessed at. Call us at 514 223-1197.
Some signs cannot wait
A head tilted to one side, loss of balance, eyes that flick on their own, a drooping eyelid or lip, severe pain, blood in the canal, hearing that disappears suddenly. These signs can mean the problem has gone deeper than the canal, or has reached the nerve of the face. One of them is enough to call straight away: you do not have to work out which one matters most.
See the full listWhat is otitis externa?
Otitis externa is inflammation of the ear canal: the tunnel running from the ear flap down to the eardrum. It is the part of the ear you can reach from outside, and by far the part most often affected. Hold on to one thing right away, because it explains everything else on this page: in adult dogs, ear infections are almost always secondary. Something inflamed the canal first, and the infection moved in afterwards.
A canal shaped like an L
A dog's ear canal is not a straight hole. It runs down vertically along the side of the head, then turns inward, horizontally, before reaching the eardrum. That bend has three very practical consequences.
You cannot see the eardrum
Nobody can, with the naked eye, you or us. It takes an otoscope, and it takes a canal clear enough to let the light through.
What goes down does not come back up
Debris pushed downward stays down there. That is exactly why cotton swabs make things worse instead of better.
A closed tube, warm and damp
An environment where a yeast or a bacterium that was living quietly in small numbers starts multiplying the moment inflammation gives it the chance.
Otitis does not mean infection
A perfectly normal ear already has bacteria and yeast in it. They belong there, in small numbers, and they bother nobody. What starts an ear infection is inflammation: the canal reddens, swells, produces more wax, and suddenly becomes a place where those organisms can multiply. So the infection is usually step two, not step one. That distinction sounds academic and is nothing of the sort: if you treat the infection without dealing with whatever lit the inflammation, you put out the smoke and leave the fire.
Three floors, and this page is about the first
The ear has three levels. The outer ear, the canal, which is what this page is about. The middle ear, behind the eardrum. The inner ear, deepest of all, which holds hearing and balance. A neglected or long-running outer ear infection often reaches the floor below, and the signs change completely at that point: it is no longer an itchy ear, it is a dog tilting his head and losing his balance.
The signs, and what they do not tell you
Most owners arrive with the same sentence: "he will not stop shaking his head". It is often the very first sign, and it shows up before the ear looks like anything at all from the outside.
What you see at home
- He shakes his head, over and over, often with a flapping sound.
- He scratches at the ear with a hind foot, or rubs the side of his head on the rug, the couch, your leg.
- The ear smells. Sweet, sour or frankly bad, sometimes noticeable from across the room.
- There is discharge: brown, near black, yellow, sometimes as thick as paste.
- The ear flap or the opening of the canal is red, hot, swollen.
- He holds one ear lower than the other, or turns his head away when your hand comes near.
- He no longer wants his head touched, when he used to love it.
- Often all of this on one side only. A one-sided ear infection is completely ordinary, and no milder for being one-sided.
What the smell and the color do not tell you
There are a lot of shortcuts in circulation: brown means yeast, yellow means bacteria, a given smell means a given thing. It is not true, and it is not true for us either. The color of the discharge and the smell of the canal do not reliably tell anyone what is growing in that ear. A swab under the microscope answers it; the nose and the eye do not. This limit is not a technicality: it is why treatment chosen without a swab can miss, and why an ear infection that "does not respond" is very often an ear infection treated for the wrong organism.
Things that look like an ear infection and are not
- An ear flap swollen, hot and tight like a cushionThat is an aural hematoma: blood that has collected inside the flap, almost always from head shaking. It needs to be seen, and the ear that caused it needs treating too.
- A dog shaking his head violently on one side, all at onceEspecially after a walk through tall grass. Think plant foreign body. It does not wait: removing it is a clinic job.
- A canal full of dry black debris in a puppy or a young dogEspecially one from a breeder or a shelter. Ear mites are more common in young animals, and they spread to other pets in the house.
- A tilted head, a dog who staggersAt that point the outer ear is no longer the main subject. See the next section, and call us.
When it is more than the outer ear
An ordinary outer ear infection is painful and miserable, but it is not counted in hours. Some signs change that sentence completely. They mean the problem reaches deeper than the canal, or involves the facial nerve, which runs right past the middle ear. Call us now if you see even one of these.
- A head tilted to one side, loss of balance, walking in circles, falling.
- Eyes that flick back and forth or up and down on their own.
- A drooping eyelid or lip on one side, an eye that no longer closes fully, a pupil visibly smaller on one side only, or the third eyelid coming up across the eye.
- Severe pain: he cries when your hand comes near, he will not let you touch his head, he stops eating.
- Blood in the canal or on the cotton.
- An ear flap that has suddenly swollen, hot and tight.
- Hearing that disappears suddenly, on one side or both.
- Swelling or heat around the ear, with a dog who is flat or feverish.
Outside our opening hours we do not run an emergency service: go to a veterinary centre open 24/7, then tell us so we can take it from there.
Why those signs in particular
The nerve that drives the muscles of the face and the nerve of balance both run immediately next to the middle and inner ear. So an infection or inflammation that reaches that level can show up as a drooping eyelid, a slack lip on one side, an eye that no longer closes, a tilted head or a weaving walk. It is not a stroke, and it is rarely what the owner pictures first. But it changes the day: this gets looked at today, not next week.
If the main sign is balance or a tilted head, call first, then read our guide on My pet is losing balance or tilting their head.
Same day, without being a middle-of-the-night emergency
Between an emergency and an appointment next week, some situations mean the ear should be looked at today: pain climbing fast, an ear that was clean the day before yesterday and is running today, a dog who cannot sleep for scratching, or an ear infection that appears during treatment already underway for that same ear. Call us: triage is our job, not yours.
What not to do while you wait
Put nothing in the ear before it has been looked at. Not leftover drops from a past ear infection, not a cleaner, not something from the family medicine cabinet, not a home preparation. An ear that has not been looked at this time may have a ruptured eardrum. And do not clean an ear that is painful or discharging: our guide Cleaning the ears is explicit about that, and it is right.
And if you have already put something in: If you have already put something in the ear before calling us, put nothing more in and tell us: knowing what went in, and when, changes what we look for under the microscope and what we choose next. Nobody is going to hold that against you.
Give no home medications
An ear infection hurts, genuinely hurts, and it is usually in the evening that you notice. The temptation then is to give "something to take the edge off until tomorrow". This is the most dangerous moment on this page, so let us be precise: the painkillers in your medicine cabinet are not gentler versions of what we prescribe. They are different molecules, and several of them are toxic.
Acetaminophen (Tylenol)
In dogs it attacks the liver and the red blood cells, and the dose that does damage is not the one you would picture. In cats it is fatal, even a single tablet: there is no safe dose. If there is a cat in the house, leave nothing lying around, and if either of them has swallowed some, it is an immediate emergency.
Ibuprofen (Advil, Motrin), naproxen (Aleve), aspirin
Digestive ulcers, kidney and liver damage. Never a human anti-inflammatory, for any reason, and least of all to settle an ear that hurts. Cats are more sensitive to them than dogs, at smaller amounts.
The drops left over from a past ear infection
This is the object sitting on the counter of almost every reader of this page, so it gets its own line. An opened bottle is no longer the medication it was, it is probably no longer the same organism, and above all nobody has looked at this eardrum this time. Some ear medications become dangerous for hearing and balance once the eardrum is ruptured.
Another animal's prescription
Same apparent problem, same weight, same house: none of that is ever enough. What relieves a dog can harm a cat, and a dose calculated for another patient is not a dose.
Hydrogen peroxide, alcohol, vinegar, oil
None of these is a treatment. Several sting and inflame the canal all on their own, and several are dangerous if the eardrum is ruptured. The home recipe found online belongs on the same line.
If you have already given some
Tell us right away, without waiting for the appointment: call us, or a veterinary centre open 24/7 outside our hours. This is not a reproach, it is information we need in order to know what to watch for.
Why it is almost never just an ear infection
This is the section that matters most on this page. In adult dogs, an ear infection rarely turns up on its own: in the very large majority of cases there is an underlying cause that inflamed the canal before a single bacterium got involved. We do not always put our finger on it the first time, but it is there. Until it is identified, the ear infection will come back, and it will come back without being the treatment's fault or yours.
Four things stacked
A chronic ear infection is not one problem, it is four problems stacked. Pulling them apart is exactly what a consultation is trying to do.
- What lit the fireThe underlying cause. In adult dogs it is most often allergic skin disease.
- What makes the ear easier to inflameThe shape of the ear, moisture, hair in the canal. None of it starts anything on its own, but all of it makes everything easier.
- What settles in on topThe yeast and bacteria taking advantage of a warm, damp, inflamed canal. That is what smells, what runs, and what topical treatment targets.
- What stops it healingA canal that thickens, that narrows, a middle ear that is involved. These are the changes that make a three-year-old ear problem behave nothing like a first episode.
Treatment that only deals with point 3 works, and then the ear infection returns. That is not the medication failing: it is point 1 not having moved.
The most common underlying cause, by a wide margin
In adult dogs it is allergic skin disease: environmental allergy (atopy) above all, sometimes food allergy. And here is the part most people do not know: the ear is often the very first place that reacts, and sometimes the only one for months. A dog running through one ear infection after another without itching anywhere else is not a dog with "delicate ears". It is a very typical allergy picture, and it is often how the diagnosis finally gets made.
If you have ever thought "he only gets ear infections, his skin is fine", that is the single sentence we hear most, and it is the one that delays the diagnosis longest.
The underlying allergy has its own guide, and it is probably the page to read right after this one: Allergies in dogs.
The other underlying causes
- Food allergyLess common than atopy, itchy year round, sometimes with digestive signs alongside. There is only one way to confirm it: a strict diet trial, followed by a return to the old food to see whether the signs come back. No blood, saliva or hair test diagnoses it, including the ones sold straight to owners: they have been evaluated, and they are not reliable.
- A plant foreign bodyAbrupt, one-sided, often after time outdoors.
- Ear mitesCommon in puppies and young dogs, uncommon in adults. Contagious between pets in the household, which changes the conversation for everyone at home.
- HypothyroidismIn middle-aged to older dogs, recurring ear and skin infections are part of the picture, often with a dull coat, weight gain and a general loss of drive.
- Less oftenA mass or a polyp in the canal, or an autoimmune skin disease.
The hormonal picture has its own guide too: Hypothyroidism in dogs.
What predisposes, without causing
A lot of people stop at conformation: "he has floppy ears, that is why". It is not wrong, but it is not enough, and the nuance changes everything.
- Floppy ears, which close off the canal and hold moisture in.
- A narrow canal, or a very hairy one.
- Swimming, frequent baths, damp that never dries.
- A canal already damaged by previous ear infections.
There are thousands of floppy-eared dogs who will never have a single ear infection, and prick-eared dogs who get them anyway. Conformation makes an ear easier to inflame; it does not light the inflammation by itself. That is why we do not stop at "it is the breed": that answer is comfortable, and it leads nowhere.
If you take one sentence away from this page, take this one: an ear that keeps coming back is a symptom, not a diagnosis. The useful question is not "which drops this time", it is "what has been inflaming this ear all along".
The exam and the swab: what they decide
An ear consultation is not a quick glance followed by a prescription. Two things decide the treatment, and they are repeated at every episode, not done once and for all.
Look down the canal, with an otoscope, on both sides
We look at both ears even when only one is a problem, because the second one is very often on its way. We are assessing four things: what the canal wall looks like (red, thickened, narrowed, ulcerated), what is in it, how far down we can get, and the state of the eardrum.
An ear that hurts badly is not examined by force
An inflamed canal is painful, and a dog in pain defends himself. Forcing achieves nothing good: we see poorly, we hurt him, and we turn the ear into a battleground for every time after this one. When that is the situation, we offer sedation, sometimes anesthesia, so the exam can be complete and comfortable. That is not excess caution: it is often the only way to see the bottom of the canal and the eardrum, and therefore the only way to choose properly.
The swab under the microscope (cytology)
A swab in the canal, a smear on a slide, and a reading under the microscope in-house. It is a routine thing to do, and it is the thing that changes the treatment. It answers a question nothing else answers: what is growing in this ear, today?
- Yeast in quantity: Not the same family of treatment.
- Round bacteria, in clusters or chains: Another family again.
- Rod-shaped bacteria: This result genuinely changes the plan. These ear infections are often more painful, more ulcerated, harder to clear, and they frequently justify a culture, closer follow-up and sometimes an image of the middle ear.
- How much inflammation there is: The number of inflammatory cells tells us whether the ear is settling, independently of what it looks like from outside.
Why "the same drops as last time" is not a plan
It is the most common request on the phone, and it makes complete sense: it worked, the ear looks the same, why go through the whole thing again. Here are the three reasons, and all three hold.
- It is probably not the same organism. The flora in an ear shifts between episodes, and shifts most of all under treatment. A first episode dominated by yeast often comes back as a bacterial one. Drops that were exactly right in March can be exactly wrong in August.
- The eardrum was checked last time, not this time. An eardrum can have ruptured since, without showing it and without hurting more. Some ear medications become dangerous for hearing and balance at that point. That is what the next section is about.
- An opened bottle is no longer the medication it was. Our guide on ear medications is categorical about this and we are not going to soften it here: you never open an old bottle.
What the exam sometimes triggers as well
Depending on what the otoscope and the slide showed, the exam sometimes opens a second door. None of these four things is automatic.
- A cultureWhen rods are seen, when a well-followed treatment achieved nothing, or when the problem is reaching deeper. It is always read alongside the microscope slide, never instead of it.
- BloodworkIf the overall picture suggests a systemic cause, hypothyroidism for instance. See also our laboratory service.
- An image of the middle earWhen we suspect the problem has gone past the eardrum. Radiographs are done here, sometimes under sedation or anesthesia so the head can be positioned properly. When a finer image than a radiograph is needed, your veterinarian will tell you where it is done. See also our imaging service.
- An allergy work-upFrom the moment the ear starts recurring. That is the last section of this page.
Where the sample goes, and how long it takes
Some tests are run here, in our own laboratory, and the result sometimes comes back during the visit itself: that is the case for the ear swab under the microscope. Other samples go to an outside laboratory, a culture for instance. How long it takes depends on the test and on where it goes: ask your veterinarian which of the two applies and how long to expect, that is the question to ask when the sample is taken. Treatment does not wait for it: we start with what the slide showed, and adjust if the culture calls for it.
An ear that looks like nothing still gets looked at once a year. The annual exam is in fact where we most often catch an early ear infection, in a dog nobody had noticed was shaking his head a little. annual exam.
The eardrum first
This is the rule owners know least and the most important one on this page. Before anything goes into an ear, we look at the eardrum. Not on principle: because the consequence of a ruptured eardrum nobody saw can be permanent.
What is behind it
Behind the eardrum is the middle ear. Behind the middle ear is the inner ear, which holds both hearing and the organ of balance. The eardrum is the wall separating the canal, open to the outside, from that whole delicate level. When that wall is intact, a product poured into the canal stays there. When it is not, the product goes through.
Why that matters
Some ear medications and some cleaning solutions are safe in a closed canal and not safe at all in the middle ear. They can reach hearing or balance, sometimes permanently. That is the only reason we press on this so hard: the margin for error is not recoverable.
And nobody can guess
- You cannot see the eardrumThe bend in the canal hides it. There is nothing to look at at home, and nothing to conclude from it.
- A ruptured eardrum does not necessarily hurt moreThere is no reliable sign at home, and nothing to read into it either way: an ear that hurts less today tells you nothing about the eardrum, and neither does an ear that hurts a lot.
- The chronic ear is the one most at riskProlonged inflammation and infection weaken the eardrum. Which means the dog with the most leftover drops sitting at home is also the dog whose eardrum is most likely to be damaged.
When we cannot see the eardrum
Sometimes the canal is too full for the eardrum to be assessed at the first exam. We do not guess: we clean it in clinic first, with a product chosen to be safe even if the eardrum is not intact, and then reassess. It is one more step, and it is worth it.
What this means for you, concretely
Nothing goes into the ear until it has been looked at this time. Not the drops from the last ear infection, not the other dog's, not a cleaner bought at the pet store, no hydrogen peroxide, no alcohol, no vinegar, no oil. Our two how-to guides already say this, in detail and without ambiguity, and they are the authority on it.
If your dog is already tilting his head or losing his balance, put nothing in at all and call us. Our guide on My pet is losing balance or tilting their head explains that picture.
Treatment, and the recheck that follows
Treating an ear infection does two things at once: settle the ear now, and deal with whatever inflamed it. Skipping the second half is signing up for the next episode. The exact products are your veterinarian's call, after the exam and the swab; here are the broad families, described by what they do.
Settling the ear
- A topical treatment, chosen from what was seen under the microscope. This is the backbone. These products generally combine something to bring the inflammation down with something to target the organism identified.
- An oral anti-inflammatory, when the canal is so swollen nothing can get down it, or so painful that no treatment is possible.
- Pain relief. An ear infection hurts, genuinely hurts, and that is not a side note in the plan. What relieves it is prescribed; nothing from your medicine cabinet belongs there.
- An oral antibiotic: rarely, and not for convenience. A swallowed antibiotic reaches the outer ear canal poorly. Topical treatment is almost always more effective for the outer ear. The oral route is kept for situations that genuinely warrant it, the middle ear in particular.
- Cleaning is part of treatment, but on our schedule and with the product we chose, never improvised.
- A deep cleaning, under sedation or general anesthesia, when the canal is too full, too painful or too damaged to be treated any other way. That cleaning happens here, during our opening hours, with a video otoscope that lets us see the bottom of the canal and the eardrum while we work. During anesthesia, one member of the team does nothing but watch your pet, with the monitors the case calls for.
Dealing with the cause
- Flea control, year round, on every pet in the household. Simple, and often part of the answer.
- The allergy work-up, if this is the second or third time. That is the next section.
- A hormone panel, when the overall picture points that way.
- The foreign body or the polyp, when there is one: it comes out, and that is often what settles the problem.
The ear looks normal long before it is
This is by far the most common way an ear infection becomes a chronic one. After a few days the smell is gone, the discharge with it, the dog has stopped scratching, and putting the bottle away becomes very tempting. Except that what the canal looks like and what it actually is do not line up: an ear can look visually clean while the microscope still finds what it found at the start. Stopping at that moment lets whatever was left start over, usually more stubborn than the first time.
Give the full course, through to the date we set together, even if everything has looked fine for a week.
The recheck is not a formality
The recheck appointment exists to repeat the swab. It is the only way to know the ear is cured and not merely quiet. It is also the appointment that lets us say, on evidence rather than by feel, whether to extend treatment, change approach, or move on to hunting for the underlying cause. Ask for it at the same time as the consultation rather than afterwards: it is the appointment everybody postpones, and it is the one that prevents the next episode.
The prescribed treatment is dispensed at our pharmacy, with instructions on how to give it. If the handling worries you, our guide Ear medications walks through it step by step.
Never do this
- Stop treatment because the ear looks fine.
- Reuse an old bottle, or another pet's.
- Adjust the amount or the frequency yourself.
- Clean an ear that is painful, bleeding or discharging before it has been looked at.
- Put hydrogen peroxide, alcohol, vinegar, oil or any home preparation into an ear.
- Give a human painkiller: ibuprofen (Advil, Motrin), acetaminophen (Tylenol), aspirin. None of them is a gentler version of what we prescribe, and none of them has a home dose. See above.
When it comes back: what a third episode changes
An ear infection that comes back is not bad luck, and it is not proof that treatment does not work either. It is information, and it is probably the most useful information we have about your dog.
The threshold, and what it means
As soon as an ear infection comes back within months of clearing completely, or an ear never quite returns to normal between episodes, the conversation changes subject. We stop treating ear infections one at a time and go looking for what is causing them. Our own working marker is a third episode in twelve months, but it is not a law and nobody is counting on your behalf: two clear episodes in six months in a young dog earn exactly the same discussion.
What actually changes
- We look for the underlying cause properlyIn an adult dog that means an allergy work-up: ruling out fleas rigorously, running a strict diet trial where the picture warrants it, and assessing atopy. See also Allergies in dogs.
- We look at the hormonal sideWhen age, coat and general condition suggest it. See also Hypothyroidism in dogs.
- We assess the middle earWith a radiograph, or a finer image depending on the case, because an outer ear infection that lasts often reaches it, and a middle ear that is involved feeds the outer ear indefinitely.
- We cultureWhen the flora becomes difficult. The sample is taken here, the culture goes to an outside laboratory.
- We put a follow-up plan in placeWith scheduled rechecks rather than an urgent visit every time. That is easier to live with, for you and for the dog.
- We consider a veterinary dermatologist's opinionWhen the cause resists, and that opinion is a referral. The dermatology workup itself happens here: skin scrapings, cytology, fungal culture, and the rechecks that follow.
What is at stake if nothing changes
Let us be honest about this without turning it into a threat. Inflammation lasting years thickens the wall of the canal. The canal narrows, distorts, and in some cases eventually calcifies: at that point no topical treatment reaches its destination any more, and the ear can no longer heal. The fallback then becomes surgery that opens or removes the ear canal. Ear surgery is part of what we do here, during our opening hours; for any given case, your veterinarian will tell you how and where it is done, after looking at the ear. It is not where most dogs end up, nowhere near, and that is exactly why we push on the underlying cause instead of on a fifth round of drops.
What we can honestly promise you
If your dog is allergic, he will probably have ears to watch for the rest of his life, and you deserve to be told that straight rather than left hoping one more time that this was the last one. The goal is not "never again". The goal is: less often, less severe, caught earlier, and a plan you know how to start yourself at the first head shake. Plenty of dogs go from one ear infection after another to rare, widely spaced episodes that clear easily. That is a very good result, and it is the one we are aiming at with you.
You did not miss something. Treating one ear infection at a time is what everyone does at first, us included. What changes things is deciding, once, to look underneath.
Frequently asked questions
I have drops left from the last ear infection. Can I use them?
Can I treat this at home?
He got an ear infection after swimming. It is the water, right?
He has floppy ears. Is that why he gets ear infections?
The ear looks fine after a few days. Can I stop?
Is it contagious to my other dog, or to me?
His ear flap swelled up all at once, hot and tight like a cushion. What is it?
Could he go deaf, or end up having ear surgery?
Also worth reading
Updated September 6, 2026 · Hôpital Vétérinaire Métro Iberville
This guide is provided for informational and educational purposes only. It does not constitute veterinary medical advice and is not a substitute for a consultation with a qualified veterinarian. Every animal is unique and their health must be evaluated individually. If you have concerns about your pet's health, contact our clinic or consult a veterinarian promptly.
Worried about your dog's ear?
A painful ear has to be looked at: it is the only way to know what is in there and whether the eardrum is intact. Book an appointment, or call us if you are unsure how urgent it is.