Ear Infections in Cats: Mites, Bacteria, and Yeast, and How to Tell Them Apart

A cat shaking its head, scratching at one ear, or tilting slightly to one side is showing one of the more common reasons for a vet visit. What's actually causing it, though, varies more than most owners expect: mites, bacteria, and yeast can all produce a similar-looking mess in the ear canal, and telling them apart matters for picking the right treatment.

What's actually going on in there

Vets call this otitis externa: inflammation of the outer ear canal. VCA Animal Hospitals notes that it's rarely a standalone problem in cats the way it often is in dogs; it usually develops on top of an underlying cause, whether that's mites, allergies, excess earwax, or a foreign body like a grass seed, that lets bacteria or yeast take hold and multiply.

Ear mites: the most common cause in cats

Ear mites (Otodectes cynotis) are, according to the University of Saskatchewan's Western College of Veterinary Medicine, the single most frequent cause of ear infections specifically in cats, especially kittens and cats from shelters or large multi-cat groups. They produce a distinctive dark, crumbly discharge that's often compared to coffee grounds, a mix of ear wax, dried blood, and mite debris. VCA notes that mites are highly contagious between animals through direct contact, which is why a single infested cat in a household can spread them to every other pet fairly quickly.

Bacterial and yeast infections

Once the ear's normal balance is disrupted, whether by mites, allergies, moisture, or excess wax, bacteria or the yeast Malassezia can overgrow and take over as secondary infections. The Merck Veterinary Manual notes that these tend to produce a different look than mites: a yellow, brown, or sometimes foul-smelling discharge, along with redness, swelling, and visible discomfort when the ear is touched.

Why home guessing isn't reliable

Mites, bacteria, and yeast can all cause head shaking, scratching, and odor, and mixed infections (mites plus a secondary bacterial or yeast overgrowth) are common enough that appearance alone isn't a reliable way to tell them apart. PetMD recommends an ear swab examined under a microscope, a quick in-clinic test that identifies exactly what's present so treatment actually targets the right organism rather than guessing.

Treatment

Treatment is directed at whatever the swab finds: a parasiticide for mites, an antibiotic for bacterial overgrowth, or an antifungal for yeast, often alongside a combination ear medication and a gentle professional ear cleaning to clear out debris first. Over-the-counter ear cleaners used without a diagnosis can mask symptoms temporarily without resolving the underlying cause, and using the wrong medication for the actual organism involved tends to prolong the problem rather than fix it.

Frequently asked questions

Can I just clean my cat's ears at home instead of seeing a vet?
A mild, occasional wax buildup can sometimes be managed with a vet-approved cleaner, but active symptoms like discharge, odor, redness, or scratching are worth a proper diagnosis before treating at home.

Are ear mites contagious to other pets in the house?
Yes, they spread readily to other cats and dogs through direct contact, so treating only the symptomatic cat in a multi-pet household often isn't enough to fully resolve an infestation.

Can untreated ear infections cause lasting damage?
Yes, a chronic or severe infection can spread to the middle or inner ear and, in some cases, affect balance or hearing, which is part of why persistent symptoms shouldn't be left unaddressed for long.

Sources

• VCA Animal Hospitals, "Ear Infections in Cats (Otitis Externa)"
• Merck Veterinary Manual, "Otitis Externa (External Ear Infection) in Cats"
• PetMD, "Cat Ear Infection: Symptoms, Causes, and Treatment"
• VCA Animal Hospitals, "Ear Mites (Otodectes) in Cats and Dogs"
• University of Saskatchewan WCVM, "Otodectes cynotis"

This article is for general information and isn't a substitute for advice from your own veterinarian, who can properly diagnose and treat ear symptoms in your specific cat.