Brown Ear Discharge in Cats: 3 Causes, 2 Slides, 14 Days

Brown ear discharge comes from 3 causes, and texture tells you more than shade. Dry crumbs 1 to 2 mm across that look like coffee grounds are usually ear mites. A greasy brown paste with a sour smell is yeast. A wet brown film on red, painful skin is bacterial. Two microscope checks, a 14-day course, and a recheck at 2 weeks settle most cases.

Three causes, one table

Cause	What you see	Microscope count	Course in days	Recheck in days
Ear mites, Otodectes	Dry 1 to 2 mm crumbs, coffee-ground look	2 to 20 mites per low-power field	14	14
Yeast, Malassezia	Greasy brown paste, sour bread smell	3 or more yeasts per oil field	14	14
Bacteria	Wet brown film, red canal, pain on touch	10 or more cocci per field, or rods	10 to 14	14
Mites plus yeast	Brown paste with 5 to 10 pale specks in it	Both found on the same slide	21	14

Mites are the classic cause in cats under 2 years, and they itch hard: 10 to 30 scratches an hour with a hind leg, plus scabs at the ear base. Yeast follows mites in roughly half of untreated cases, which is why a cat treated for mites for 7 days often comes back with a worse ear at day 10.

The 2 microscope checks

The first is a wet mount. A sample of the debris goes into 1 or 2 drops of mineral oil on a slide, a cover slip goes on, and the slide is read at 10x and then 40x. Mites are 0.3 to 0.4 mm, oval, and move once the slide warms for 30 seconds; eggs are half that size and stick to the hairs. A negative wet mount does not rule mites out, because 1 in 3 cats with mites shows none on a single swab.

The second is a stained cytology. The swab is rolled onto a slide, dried, stained, and read at 400x. This is the check that counts yeasts and bacteria: 3 or more yeasts per oil-immersion field means overgrowth, and 10 or more cocci per field means infection. The 2 checks answer 2 different questions, which is why a clinic that only does one of them misses the mixed cases.

Why the course runs 14 days

A mite egg takes 3 weeks to become an adult that lays eggs, so a 7-day course kills the adults and leaves the next generation. The standard plan is 2 doses of a mite product 14 days apart, with every cat in the house treated on the same day, because mites move between cats on a brush or a shoulder within 24 hours.

Yeast needs the same 14 days for a different reason: the canal stays damp and inflamed for 10 to 14 days after the organisms are gone, and stopping at day 5 lets the population climb back within 72 hours. Bacterial cases run 10 to 14 days, and a course that stops at day 3 of a 10-day plan is the most common reason a brown ear returns inside 30 days.

What the 2-week recheck looks for

At day 14 the vet repeats the cytology and looks at the drum, which sits about 3 cm in from the opening. Three outcomes are possible: a clean slide with a visible drum means stop and recheck in 6 months; 3 or more yeasts means another 14 days and a hunt for why the canal stays wet; a drum that cannot be seen means a polyp, a foreign body, or middle ear disease, and the next step is imaging.

When to go: hour by hour

What you see	Why it matters	Go within
Head tilt of 15 degrees or more, or eyes flicking side to side	Middle or inner ear involvement	2 hours
Ear flap swollen to 5 mm or more, hot and fluid-filled	Hematoma forming	6 hours
One side of the face droops, the eye will not blink	Facial nerve damage	6 hours
Brown discharge with head shaking 20 or more times an hour	Mechanical damage adding up	48 hours
Brown discharge on and off for 90 days or more	Polyp, allergy, or middle ear disease	7 days

The 2-hour row is about balance, not discharge. A cat that circles one way, falls off a 40 cm ledge, or holds its head at 15 degrees has a problem behind the drum, where cleaner cannot reach.

Five look-alikes

Mites. Both ears in 80 percent of cases, intense itch, crumbs that move under a warm slide. Response to the first dose comes in 3 to 5 days.

Yeast. Often one ear, sour smell, brown paste that stains a cotton pad in 1 swipe. It flares after swimming or after 2 weeks of daily cleaning.

Bacteria. Pain on touch, a canal that bleeds at a swab, and a smell that carries across a room. Rods mean culture.

Polyp or foreign body. One ear, brown discharge with a pink tinge, head tilt of 10 to 15 degrees. A grass awn 3 to 5 mm long is the usual summer find.

Food or environmental allergy. Both ears, thin brown wax, no mites and fewer than 3 yeasts per field, itch that runs 6 to 8 months a year. This one needs diet work, not more cleaner.

Five things to record at home

• Photograph the discharge on a white paper towel next to a coin, once a day, so the change in volume is visible.
• Count scratches and head shakes for 1 minute, 3 times a day.
• Note the smell in plain words: sour, yeasty, rotten, or none.
• Write down which ear, and whether the cat tilts its head 5, 10, or 15 degrees.
• Keep the dates of every dose and cleaning, since a 14-day plan fails most often at day 5.

What to do this week

1. Look at the discharge on paper, not in the ear: crumbs, paste, or film decides the first question.
2. Ask for both microscope checks, the oil prep and the stained slide, on the first visit.
3. Treat every cat in the house on the same day if mites are found.
4. Set a phone reminder for day 7 and day 14, because the second dose is the one that works.
5. Book the recheck for day 14 and bring the photo log, so a relapse at day 10 is visible.

For the color-by-color breakdown see ear discharge types and discharge colors; if a plant or a human product got into the ear, check the toxic list before you clean again.

Terms mentioned in this article

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