A cat with an ear infection typically has visibly red, swollen ear canals and some type of discharge, ranging from dark and waxy to yellow and pus-like depending on the cause. You may also notice your cat shaking its head repeatedly, scratching at one or both ears, or flinching when you touch the area around its ears. These signs can develop gradually or seem to appear overnight, but they all point to inflammation inside the ear canal that needs veterinary attention.
What You’ll See Inside the Ear
The most obvious sign is a change in what the inside of your cat’s ear looks like. Healthy cat ears are pale pink, relatively dry, and have little to no visible wax. An infected ear looks noticeably different. The skin lining the ear canal becomes red and swollen, sometimes enough to partially block the canal itself. You might see the ear flap (the outer part you can touch) look puffier than usual, and the skin may appear irritated or flaky.
Discharge is the other hallmark. The type of discharge actually tells you something about what’s going on:
- Black, waxy buildup that resembles coffee grounds: This is the classic look of ear mites, tiny parasites that thrive in the ear canal. The dark debris is a mix of wax, mite waste, and dried blood.
- Yellow or greenish, pus-like discharge: This points toward a bacterial infection. It often has a strong, unpleasant smell.
- Brown, greasy discharge: Yeast overgrowth tends to produce this type. Yeast (specifically a species called Malassezia) exists in small numbers in healthy cat ears but can multiply rapidly when conditions change, creating a thick, oily buildup with a musty odor.
In some cases, the ear simply smells bad before you see much visible change. A foul odor coming from one or both ears is worth investigating even if the ear doesn’t look dramatically different yet.
How Your Cat Will Act
Behavioral changes often show up before you get a close look at the ears. Cats with ear infections experience intense itching and discomfort, which drives a few characteristic behaviors. Frequent head shaking is one of the most common. Your cat may shake its head dozens of times a day, far more than the occasional shake that’s normal. Persistent scratching at one or both ears is another reliable sign, and you may notice scratch marks or hair loss around the base of the ear from all the pawing.
Some cats tilt their head to one side, favoring the infected ear. Others flatten their ears against their head or pull away when you try to touch the area. A cat that normally enjoys having its head rubbed but suddenly resists contact around the ears is telling you something. In more severe infections, cats can become lethargic or lose interest in food because the pain and irritation are constant.
Ear Mites vs. Bacterial and Yeast Infections
Ear mites are extremely common in cats, especially kittens and cats that spend time outdoors or live with other animals. The thick, dark, crumbly debris they leave behind is distinctive enough that many cat owners recognize it on sight. Mite infestations also tend to affect both ears at the same time and cause relentless scratching.
Bacterial and yeast infections often develop as secondary problems. Allergies, moisture trapped in the ear canal, or damage from mites can all create an environment where bacteria or yeast multiply out of control. These infections tend to produce wetter, smellier discharge compared to the dry, dark buildup of mites. Bacterial infections caused by certain rod-shaped bacteria can be especially stubborn and produce a greenish discharge with a particularly foul smell. Your vet can distinguish between these causes quickly by swabbing the ear and examining the sample under a microscope, where bacteria, yeast cells, and mites each look distinctly different.
What Happens If It Goes Untreated
Left alone, ear infections don’t just persist. They get worse in ways that create new problems. One of the most dramatic complications is an aural hematoma. When a cat scratches at an infected ear aggressively or shakes its head hard enough, blood vessels inside the ear flap rupture. Blood pools between the layers of cartilage with nowhere to drain, and the ear flap swells up like a small balloon. According to Cornell University’s veterinary team, a hematoma can resolve on its own, but that process takes weeks, and the cartilage heals into a deformed, bumpy shape, leaving the cat with a permanently crumpled “cauliflower ear.”
The infection itself can also spread deeper. Outer ear infections (in the visible canal) can progress inward, potentially damaging the eardrum. Once the eardrum is compromised, infection can reach the middle and inner ear, causing balance problems, a noticeable head tilt, and in severe cases, hearing loss. These deeper infections are significantly harder and more expensive to treat than a straightforward outer ear infection caught early.
What the Vet Visit Looks Like
A vet will start by looking into the ear canal with an otoscope, a handheld device with a light and magnifying lens. This shows how swollen the canal is, whether there’s significant debris buildup, and whether the eardrum is intact. Next, they’ll gently swab the ear canal and roll the sample onto a glass slide. After staining it, they examine it under high magnification to identify exactly what’s growing in there: yeast cells, specific types of bacteria, or mites. This step matters because the treatment is different depending on what’s causing the problem.
Treatment typically involves medicated ear drops that target the specific organism involved, often combined with a steroid component to reduce swelling and itching. Your vet will likely clean the ears during the visit to remove built-up debris so the medication can actually reach the infected tissue. Expect the full course of treatment to take several weeks. Stopping early because the ear looks better is one of the most common reasons infections come back, since the organisms can still be present even after visible symptoms improve. Follow-up visits to recheck the ear under a microscope help confirm the infection is truly resolved.
Cats Most Prone to Ear Infections
Any cat can develop an ear infection, but some are more susceptible. Cats with allergies, whether to food or environmental triggers, are particularly prone because allergic inflammation inside the ear canal creates the warm, moist conditions that bacteria and yeast love. Cats that go outdoors pick up ear mites more easily from contact with other animals. Kittens are especially vulnerable to mites simply because their immune systems are still developing. Cats with narrow ear canals or those who produce excess wax also tend to have recurring issues, since debris doesn’t drain as easily and creates a breeding ground for infection.