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Senior Dog Ear Infections: Why They Recur, and the Cause Most Owners Miss

Senior Dog Ear Infections: Why They Recur, and the Cause Most Owners Miss

By Sarah Bennett · Last updated July 20, 2026 · 9 min read

I write as a researcher and owner, not a veterinarian. A painful, red, or smelly ear needs a vet, both to treat it and to find out why it keeps happening. Nothing here replaces that exam.

The short version: A single ear infection is common. A senior dog whose ears keep getting infected, month after month, is telling you something else is going on, because recurrent ear infections are almost always a symptom of an underlying cause, not the whole problem. In late summer the trigger is often allergies (pollen, humidity, and moisture from swimming all peak now), which inflame the ear canal and let yeast and bacteria take over. But in an older dog there is a cause many owners and even some treatment plans miss: hypothyroidism, which quietly drives repeat skin and ear infections. The tell is whether she is itchy. Treat the infection, yes, but if it keeps coming back, the real fix is finding and treating what is underneath.

Why Do Senior Dogs Get Ear Infections?

A dog's ear canal is shaped like an L, which traps moisture and warmth, a setup that yeast and bacteria love. Most ear infections are not a disease in themselves; they are an overgrowth of the yeast and bacteria that already live in the ear, triggered by something that upset the ear's normal balance. That trigger is the part that matters, especially in a senior dog.

The common triggers:

  • Allergies, the single most common underlying cause of chronic ear infections. Environmental allergies (pollen, dust, mold) and food sensitivities inflame the skin lining the ear canal, and inflamed skin grows infection.
  • Moisture, from swimming, baths, or humid weather, which is why infections spike in summer.
  • Endocrine disease, especially hypothyroidism in older dogs, which changes the skin and weakens its defenses (more on this below).
  • Ear anatomy and hair, floppy ears and hairy canals hold in more moisture and heat.
  • A foreign body or growth, like a grass seed or, in seniors, a polyp or tumor in the canal, which a vet needs to rule out when one ear keeps flaring.

The key idea for an older dog: if the ear keeps getting infected, the ear is rarely the root problem. It is the place the root problem shows up.

Why Late Summer Is Peak Season

If your dog's ears flare in August, the timing is not a coincidence. Late summer stacks up several triggers at once:

  • Allergens peak. Late-summer pollens (ragweed and grasses) and mold are at their height, and allergy-driven ear inflammation rises with them.
  • Humidity and heat keep the ear canal damp and warm, the exact conditions yeast thrives in.
  • Swimming and baths trap water in the canal. Water left in a warm ear is an invitation.

Ear infections are one of the most common reasons dogs are seen by a vet, and clinics tend to see more of them in the warm, humid stretch of late summer, when the triggers above stack up. For a senior dog, whose skin barrier and immune defenses are already less robust, that seasonal load tips over into infection more easily.

The Cause Most Owners Miss: Hypothyroidism

Here is the part that separates senior ear care from the standard advice. In an older dog with recurrent skin and ear infections, an underactive thyroid is a common and under-recognized driver. Hypothyroidism alters the skin in ways that set up infection: it changes keratinization and sebum production and lowers the skin's immune defenses, so yeast and bacteria take hold again and again no matter how many times you clear the ear (Cornell Riney Canine Health Center; PetMD, on hypothyroidism and recurrent skin and ear infections).

There is a clinical clue that helps you and your vet tell the difference, and it is worth knowing:

  • Allergy-driven infections are itchy. The dog with allergies scratches, rubs, and licks, itch is the main event.
  • Hypothyroid infections are usually not very itchy. A hypothyroid dog can have recurrent ear and skin infections with a poor coat, weight gain, and low energy, but she is often minimally itchy between flares.

So a senior dog with ears that keep getting infected, who is also gaining weight, slowing down, or losing coat quality, but who is not especially itchy, is a dog whose thyroid is worth testing. Hypothyroidism is diagnosed with a blood test and treated with a daily hormone pill, and treating it is often what finally stops the ear infections. Our guide to hypothyroidism in senior dogs walks through the full picture. This is exactly the kind of underlying cause that turns "another course of ear drops" into a real fix.

Signs Your Senior Dog Has an Ear Infection

Catch it early and it is a much smaller problem. Watch for:

  • Head shaking or tilting
  • Scratching or pawing at the ear
  • Redness or swelling inside the ear flap
  • A yeasty, sour, or foul smell
  • Brown, yellow, or waxy discharge
  • Pain when you touch the ear, or holding the head to one side
  • New reluctance to be petted on the head

A sudden head tilt with loss of balance is different, that can be an inner-ear problem or vestibular disease, and it needs a same-day vet visit rather than ear cleaner.

What to Do (and What Not to Do) at Home

The honest rule with ears: home care is for prevention and mild maintenance, not for treating an active, painful infection.

Do:

  • See the vet for an active infection. They look in the ear (an intact eardrum matters for which medication is safe), identify whether it is yeast, bacteria, or both, and prescribe the right treatment. Guessing wrong wastes weeks.
  • Dry her ears after swimming or baths. A gentle wipe of the outer canal with a cotton pad, or a vet-recommended drying solution, removes the moisture infections need.
  • Use a vet-approved ear cleaner for maintenance, at the frequency your vet suggests for a dog prone to infections.
  • Keep the hair around the canal trimmed if your vet advises it, for airflow.

Do not:

  • Do not use cotton swabs down into the canal. You push debris deeper and can damage the eardrum.
  • Do not pour in home remedies like vinegar or hydrogen peroxide on an active or raw ear. They sting inflamed skin and can make things worse.
  • Do not just re-treat the same infection over and over. If it keeps coming back, the answer is to find the underlying cause, allergies or thyroid, not to keep buying drops.

Breaking the Cycle of Recurrent Ear Infections

If your senior dog is on her third or fourth ear infection of the year, the goal shifts from treating ears to finding why. A vet's approach usually works through the layers:

  1. Treat the current infection fully, and recheck to confirm it actually cleared, not just looked better.
  2. Investigate allergies, the most common driver, through diet trials or environmental management, since controlling the allergy controls the ears.
  3. Test the thyroid in an older dog, especially with the non-itchy, coat-and-weight pattern above.
  4. Rule out a growth or polyp if it is always the same ear.

Getting to the cause is what ends the cycle. It is also kinder and cheaper than a standing subscription to ear drops.

Frequently Asked Questions

Why does my old dog keep getting ear infections? Recurrent ear infections are almost always a symptom of an underlying cause rather than a problem confined to the ear. In senior dogs the usual drivers are allergies (the most common), trapped moisture, and hypothyroidism. If the infections keep returning, the fix is to find and treat that underlying cause, not just to re-treat the ear.

Can allergies cause ear infections in dogs? Yes. Allergies are the single most common underlying cause of chronic ear infections. Environmental allergens and food sensitivities inflame the skin lining the ear canal, and that inflamed skin lets yeast and bacteria overgrow. Ear flares that track with the seasons, especially late summer, often point to environmental allergies.

Could my senior dog's ear infections be a thyroid problem? They could. Hypothyroidism is an under-recognized cause of recurrent skin and ear infections in older dogs, because it weakens the skin's defenses. The clue is that hypothyroid dogs are usually not very itchy, and often have weight gain, low energy, and a dull coat alongside the infections. A blood test can check, and treating the thyroid often stops the cycle.

How can I treat my senior dog's ear infection at home? You should not treat an active infection at home; a painful, red, or smelly ear needs a vet, who checks that the eardrum is intact and prescribes the right medication. Home care is for prevention: drying the ears after swimming and using a vet-approved cleaner at the frequency your vet recommends. Never use cotton swabs in the canal or pour in vinegar or peroxide.

Are ear infections more common in summer? Yes. Warmth, humidity, peak late-summer allergens, and swimming all trap moisture and inflame the ear canal, and clinics tend to see more ear infections in the late-summer months. Senior dogs, with less robust skin and immune defenses, tip into infection more easily under that seasonal load.

Sources

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About the Author

Sarah Bennett researches senior dog care from a home centered on her Border Collie, Lucy. I am not a veterinarian; I write from a researcher and owner's perspective and check what I can against published veterinary sources, including the Cornell and PetMD material on the thyroid link cited above. The reason I lead with the underlying cause on senior dog ear infections is that the ear is usually the symptom, and for an older dog the cause worth ruling out, hypothyroidism, is the one that standard "clean and treat" advice tends to skip.

Leo Bennett co-writes Senior Dog Daily with Sarah, sharing the research and the writing.