If your dog is shaking their head, scratching at one ear, or the ear smells off, there’s a good chance it’s an ear infection — one of the most common reasons dogs end up at the vet. The good news: most are straightforward to treat once you catch them early. The bad news: left alone, they get painful fast and can become chronic.
The Three Signs That Usually Show Up First
- Head shaking or tilting. A dog trying to dislodge discomfort or fluid from the ear canal.
- Scratching at the ear or rubbing the side of the face on furniture or the floor.
- A smell — often described as yeasty, musty, or sour — coming from the ear itself.
Beyond that, look for redness or swelling inside the ear flap, dark discharge (brown, black, or yellow), visible head-tilting toward the affected side, and — in dogs who tolerate ear handling less and less — flinching or growling when you touch the area. Chronic or severe cases can also cause a loss of balance or unusual eye movements, which point to a deeper or middle-ear infection and need a vet visit without delay.
Why Dogs Get Ear Infections
According to veterinary dermatology references (including guidance published by the American College of Veterinary Dermatology), the vast majority of canine ear infections are secondary — meaning something else set the conditions for bacteria or yeast to take over. The usual suspects:
- Allergies (environmental or food) are the single biggest underlying cause. Allergic skin inflammation changes the ear canal environment and makes it more hospitable to overgrowth.
- Moisture trapped in the canal — after swimming or bathing, especially in dogs with hair inside the ear canal.
- Ear anatomy. Breeds with floppy ears (Cocker Spaniels, Basset Hounds, Labradors) or narrow, hairy canals (Poodles, Shih Tzus) trap heat and moisture more easily and are overrepresented in vet visits for ear disease.
- Ear mites, more common in puppies and cats than adult dogs, but still a possibility, especially in multi-pet households.
- Foreign material — grass seeds and debris are a classic cause of sudden, one-sided ear pain, particularly after a dog has been in tall grass or brush.
Yeast (usually Malassezia) and bacteria (often Staphylococcus or Pseudomonas) are the organisms actually causing the infection, but they’re rarely the root cause — which is why infections that get treated with drops alone, without addressing the underlying trigger, tend to come back.
What the Vet Visit Actually Involves
A vet will typically look inside the ear canal with an otoscope to check the eardrum and rule out foreign material, then take a swab to examine under a microscope. This step matters more than it might seem: yeast, bacteria, and mixed infections are treated with different medications, and guessing wrong wastes time and prolongs your dog’s discomfort. For infections that keep recurring, a vet may also recommend allergy testing or an elimination diet trial, since treating the ear alone without addressing an underlying allergy is why some dogs cycle through infections every few months.
Treatment is usually a topical ear medication (combining an antifungal, antibiotic, and anti-inflammatory) applied for one to two weeks, sometimes alongside an ear-cleaning routine at home. Severe or chronic cases may need oral medication or, rarely, imaging to check for middle-ear involvement.
What You Can (and Can’t) Do at Home
If you catch mild redness or a faint smell early, a vet-approved ear cleaner used after baths or swims can help — but only if the eardrum is intact, which you can’t confirm without a vet checking first. Do not use cotton swabs inside the canal (they pack debris deeper rather than removing it), and don’t reach for human ear drops or hydrogen peroxide, which can be irritating or ototoxic.
If your dog is prone to ear infections — swimmers, floppy-eared breeds, allergy dogs — routine drying of the ears after water exposure and periodic vet-recommended cleaning are the most effective prevention tools available. This is also where diet matters: if allergies are driving the recurrence, working through the food label with your vet to identify and remove a trigger ingredient can cut down on infections far more effectively than treating each flare-up as it comes.
When to See a Vet
See a vet within a day or two if you notice head shaking, scratching, odor, or discharge — waiting tends to let mild infections become painful ones. See a vet immediately if your dog shows loss of balance, a persistent head tilt, unusual eye movement, or pain severe enough that they won’t let you near the ear at all — these can indicate the infection has reached the middle or inner ear, which is a different, more serious problem than a routine outer-ear infection.
Chronic ear infections — three or more in a year — are a signal to look past the ear itself. That pattern is a classic marker of an underlying allergy, and it’s worth raising with your vet directly rather than just requesting another round of drops. If you’re also noticing itchy skin or paw-licking alongside the ear issues, that’s consistent with allergic disease and worth mentioning at the same appointment — as covered in our piece on why dogs get so itchy.
The Takeaway
A single ear infection after a swim is common and usually easy to clear up. Recurring infections are the ones that deserve real attention — not more drops, but a conversation with your vet about what’s driving them. Catching the pattern early saves your dog months of discomfort and saves you a lot of repeat vet visits.