Cat Ear Discharge: 4 Types by Color and Smell

Ear discharge runs to 4 types, and color plus smell does most of the sorting before any test. Dark brown and crumbly is usually ear mites. Yellow-brown and greasy, with a sour or yeasty smell, is Malassezia. Yellow pus with a painful ear is bacterial. Black and bloody means trauma until proven otherwise. A 1-minute otoscope look and a cytology slide settle the rest.

The 4 discharge types at a glance

Discharge	Smell	Usual cause	Diagnosis	Resolve in
Dark brown, dry, crumbly, 1 to 2 mm grains	Faint, earthy	Ear mites (Otodectes)	Otoscope, mite seen at 10x	3 to 4 weeks
Yellow-brown, waxy, greasy	Sour, yeasty, like bread	Malassezia yeast overgrowth	Cytology, 3 or more yeasts per field	2 to 3 weeks
Yellow to green pus, 1 to 3 mL	Rotting, sharp	Bacterial otitis, often middle ear	Cytology plus culture if it recurs	7 to 14 days
Black-red, crusted, 2 to 5 mm	Metallic	Scratch injury, polyp, tick	Otoscope, look behind the drum	24 to 48 hours
Brown paste with 5 to 10 white specks moving	Faint	Mites plus secondary yeast	Otoscope, both found on cytology	3 to 4 weeks

Two numbers decide how fast you act. A cat that shakes its head 20 or more times an hour is doing mechanical damage with every shake, and a hematoma can form in 3 days. A cat with a head tilt of 15 degrees or more, or nystagmus, has middle or inner ear involvement and needs a vet the same week, not a bottle of cleaner.

Dark brown crumbs: ear mites

Mite debris looks like coffee grounds packed in the vertical canal; the mites are 0.3 to 0.4 mm white specks that move once the sample is warmed for 30 seconds. The itch is intense: 10 to 30 scratches a minute with a hind leg is typical, with scabs at the ear base.

Treatment has to run 3 to 4 weeks, because the egg-to-adult cycle is about 3 weeks and a 7-day course leaves the next generation alive. Most vets use a spot-on every 2 to 4 weeks for 2 doses, or 1 long-acting dose, and treat every cat in the house the same day. Clean the canal 2 to 3 times a week during treatment, not 2 to 3 times a day: over-cleaning keeps the canal wet and feeds the yeast that follows mites in half of cases.

Yellow-brown and greasy: Malassezia

Yeast otitis leaves a waxy yellow-brown coat and a smell that hits you at 30 cm. It rarely comes alone: allergies, food reactions, and 2 or more weeks of antibiotic drops all push the canal toward yeast. Cytology at 400x showing 3 or more oval yeasts per field is the usual threshold for treating.

Most vets prescribe an antifungal drop twice a day for 7 to 14 days, then once a week for 3 to 4 weeks. If the ear is back to greasy within 2 weeks of stopping, the trigger was never fixed, and the next step is a food trial of 8 to 12 weeks or allergy testing rather than a third round of drops.

Yellow pus and pain: bacterial otitis

Bacteria turn the discharge yellow to green and make the ear so sore that the cat pulls away when you touch the base. Pain on opening the mouth, or a swelling under the ear, means the infection has reached the middle ear, and the drum is likely ruptured. Most vets sample for cytology first: cocci and rods need different drugs, and a 7-day blind course fails in 2 to 3 out of 10 ears.

Never use a steroid ear product on a ruptured drum, and never use a dog product: 1 dose of permethrin dog spot-on can cause tremors in a cat for 48 to 72 hours. If that happened, keep the label and check the toxin list for the active ingredient first.

Black and bloody: trauma first

Blood mixed with wax dries to a black-red crust, and in 8 out of 10 cases the cat made it itself, scratching at mites or an itch. A tick in the canal, a grass seed, or a polyp 3 to 6 mm across also bleeds, and a polyp needs removal rather than drops.

The complication is the hematoma: a 5 to 15 mm pocket of blood between cartilage and skin, usually on the flap, appearing 1 to 3 days after violent head shaking. Under 3 days old it can be drained and stitched; after 5 to 7 days the clot organizes and the ear tends to heal crumpled.

Otoscope and cytology: what each one answers

The otoscope answers structure: is the canal 4 to 6 mm wide or narrowed to 1 to 2 mm by swelling, is the drum intact, is there a mass. Cytology answers biology: mites, yeast, cocci, rods, or inflammatory cells, counted per field at 400x. Neither replaces the other, and a clinic that only looks will miss the yeast under the mites.

Do not dig at the canal with a cotton bud: a cat canal bends almost 90 degrees within 1 to 2 cm of the opening, so a bud pushes debris toward the drum. If the ear is closed by swelling to 1 to 2 mm, stop cleaning and book the visit, because a 2 mm canal cannot be cleaned safely without sedation.

Cleaning: 2 to 3 mL at 37 C, 2 to 3 times a week

Warm the bottle in your hand for 5 minutes, or stand it in water at 37 to 38 C, because cold solution against a drum causes pain and head shaking. Fill the canal with 2 to 3 mL, massage the base for 20 to 30 seconds, let the cat shake, then wipe only what you can see with gauze. Twice a week keeps a healthy ear clear; 2 to 3 times a week is the treatment schedule; every day is too much for most cats.

Skip it if the drum might be ruptured, and skip alcohol or vinegar mixes, which sting an inflamed 1 mm canal. A cat that needs weekly cleaning for 4 weeks has an underlying problem, not a hygiene problem.

The 3-day hematoma window

• Photograph the ear flap daily and measure the swelling in mm at the widest point.
• Book within 72 hours if a soft 5 mm pocket appears and the cat shakes 20 or more times an hour.
• Treat the itch at the same time: mites, yeast, or allergy, or the other ear follows in 2 to 4 weeks.
• Use a cone for 7 to 10 days after any drainage, since 1 scratch can refill the pocket overnight.

Discharge that returns within 2 weeks of finishing drops, any blood, a head tilt, or a cat that stops eating means the problem is deeper than the canal. Long-standing one-sided discharge also deserves a look at the nose and eye on that side, and the eye discharge guide covers the Horner syndrome pattern that shows up with middle ear disease. For the full mite and infection protocol, the ear mite guide lists the products and the 3-week retreatment schedule.

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