Dog eye discharge: what the color means and when to worry

Your dog wakes up with a dark crust in the corner of one eye. Normal, or something to worry about? Most of the time, dog eye discharge is just dried tears, but its color, amount and whether it affects one eye or both say a lot about what's going on.

Eyes are unforgiving: a corneal ulcer can get worse within hours, and untreated dry eye eventually damages vision. This guide gives you a table to decode discharge by appearance, the most common causes, how to clean your dog's eyes the right way, what never to put in them and when it's an emergency.

Is eye discharge normal in dogs?

Yes, in small amounts. Tears constantly clean and protect the eye and drain into the nose through the tear duct. During sleep, some of that tear film, mixed with mucus, dust and cells, collects and dries in the inner corner of the eye. The result is a small clear, grayish or dark brown crust (often called "eye boogers") that wipes away easily.

What's not normal:

Discharge that's heavy or comes back within a few hours of cleaning.
Yellow or green color, or sticky white mucus.
Constant tearing that keeps the fur wet.
Discharge with a red eye, squinting, swollen eyelids or rubbing.
Discharge in just one eye that shows up suddenly.

What the color of dog eye discharge means

What you see	Possible causes	What to do
Small clear or dark brown crust in the inner corner after sleep	Normal: dried tears and dust	Wipe daily as needed
Heavy clear tears, wet eye	Epiphora: irritation, allergies, hairs rubbing the eye, a blocked tear duct or eye pain	See your vet if it lasts more than 1–2 days or comes with squinting
Reddish-brown stains below the eye	Chronic tearing that tints light-colored fur	Have your vet look for the cause; clean daily
Thick, sticky white or gray mucus	Allergic conjunctivitis, or dry eye if it's stringy and the eye looks dull	Vet visit within a few days
Yellow or green (pus)	Bacterial infection, often on top of dry eye, an ulcer or a foreign body; in unvaccinated puppies, possibly distemper	Vet within 24–48 hours; sooner if painful
Bloody	Injury, a foreign body or a clotting problem	Emergency

The table is a guide, not a diagnosis. Several problems can produce the same discharge, and they often overlap, such as dry eye that becomes infected.

Common causes of eye discharge in dogs

Conjunctivitis

Conjunctivitis is inflammation of the conjunctiva, the pink tissue lining the eyelids and covering the white of the eye. The eye looks red, the lids may be a bit puffy and discharge ranges from clear to pus-like. In dogs, conjunctivitis is usually a sign of another problem: allergies (often alongside itchy skin; see why is my dog so itchy), irritants like smoke or dust, foreign bodies, dry eye or infection.

In puppies and unvaccinated dogs, green discharge from both eyes along with a runny nose, cough, fever or lethargy can be a sign of distemper, a serious disease that core vaccines prevent; check where your dog stands on the dog vaccination schedule.

Dry eye (keratoconjunctivitis sicca, or KCS)

With dry eye, the glands don't make enough of the watery part of tears, so the eye surface dries out and responds by producing mucus. Classic signs are thick, stringy white or yellowish discharge that returns soon after cleaning, a red eye, a dull or cloudy look and, over time, dark pigment spreading across the cornea.

It's more common in West Highland white terriers, cocker spaniels, English bulldogs, shih tzus, pugs and Cavalier King Charles spaniels. Your vet diagnoses it with a quick, painless test (the Schirmer tear test), and most dogs need lifelong treatment prescribed by the vet. Left untreated, it can lead to ulcers and vision loss.

Corneal ulcer

A corneal ulcer is a scratch or erosion on the cornea, the clear front layer of the eye. It's very painful, so your dog squints or keeps the eye closed, tears up, rubs the eye and avoids bright light. You may see a cloudy or bluish spot. Ulcers follow scratches from cats, thorns or branches, foxtails, eyelashes or eyelids that rub the eye, or dry eye. Flat-faced breeds such as the French bulldog, pug and shih tzu are at higher risk because their eyes are more exposed.

A deep ulcer can rupture the eye quickly, so it always warrants an urgent visit.

Epiphora and tear stains

Epiphora means tears overflowing the lids and soaking the fur. It happens when the eye makes too many tears (irritation, hairs or lashes rubbing, eyelids rolling inward) or when tears don't drain well (a narrow or blocked tear duct, shallow eye sockets).

In light-coated dogs like Maltese, bichons, poodles and shih tzus, tears leave reddish-brown stains under the eyes. These come from natural pigments in tears called porphyrins, which tint the fur as they oxidize. When the area stays damp, yeast can grow, darkening the fur further and causing an odor.

Other causes

Foreign bodies like grass seeds that hide behind the third eyelid; in summer, see our guide to grass awns and foxtails in dogs.
Eyelid problems: entropion (lid rolling inward), ectropion (lid drooping outward) or misplaced eyelashes.
Cherry eye, a prolapsed third-eyelid gland that looks like a red bump in the inner corner.
Glaucoma and uveitis: a red, painful eye with a cloudy cornea or an abnormal pupil. Both are emergencies.

When eye discharge is an emergency

Eye problems progress fast, and some damage can't be undone. When in doubt, have it checked sooner rather than later.

How to clean your dog's eyes step by step

You'll need sterile gauze pads (better than cotton balls, which shed fibers) and sterile saline. Cooled boiled water works if you don't have saline.

Wash your hands before and after.
Soak a gauze pad in saline. Use a fresh pad for each eye so you don't spread a possible infection.
Soften dried crusts by holding the damp pad against them for 10–20 seconds. Don't pick or pull.
Wipe from the inner corner outward, gently, without pressing on the eyeball or touching the cornea.
Dry the surrounding fur with a clean pad; constant moisture worsens staining and irritation.
Reward your dog with a favorite treat so cleaning becomes a positive routine.

For dogs with normal discharge, clean whenever crusts appear. For breeds prone to tearing, once or twice a day. Keep the hair around the eyes short with round-tipped scissors or at the groomer.

What your vet will do

Beyond examining the eyes and lids with a light, your vet may run a few quick, painless tests:

Schirmer tear test: a paper strip tucked under the lid for one minute measures tear production.
Fluorescein stain: a dye that turns corneal ulcers green and shows whether the tear ducts drain.
Eye pressure measurement: rules out glaucoma.
Cytology or culture of the discharge if infection or an unusual cause is suspected.

Treatment depends on the cause: specific eye drops or ointments, removing a foreign body, eyelid surgery in some cases or managing an underlying disease. Your dog may need a cone to prevent rubbing while the eye heals.

How to prevent eye discharge and tear stains

Clean daily if your dog is a flat-faced breed or has light or long fur around the eyes.
Keep facial hair trimmed so it doesn't poke the eye.
Check the eyes after walks during foxtail season, including the corners and under the lids.
Don't let your dog ride with their head out the car window: dust, bugs and dry wind irritate the eyes.
Stay current on vaccines and parasite prevention, and keep allergies under control.
Get a yearly vet exam that includes the eyes, especially for breeds prone to dry eye.

For what to do right away after an eye injury, keep our dog first aid guide handy.

Frequently asked questions

Can I clean my dog's eyes with chamomile tea?

It's better not to. Tea isn't sterile, can leave tiny particles in the eye and causes irritation or allergic reactions in some dogs. Single-use sterile saline is just as easy, inexpensive and safer. And if discharge doesn't improve with normal cleaning, the underlying problem won't be solved by a home remedy.

Is my dog's conjunctivitis contagious?

It depends on the cause. Allergic conjunctivitis and conjunctivitis from irritants or dry eye aren't contagious. Infectious forms, such as those that come with kennel cough or distemper, can spread to other dogs. Spreading to people is very uncommon, but always wash your hands after cleaning your dog's eyes and use a separate pad for each eye.

Why is there discharge in only one of my dog's eyes?

Problems in one eye usually have a local cause: a foreign body like a foxtail, a scratch or ulcer, an eyelash rubbing the eye or a blocked tear duct on that side. Body-wide causes such as allergies or viral infections tend to affect both eyes. That's why sudden discharge in just one eye deserves a prompt exam.

How do I get rid of tear stains on a white dog?

Start by having your vet look for the cause of the tearing, such as hairs rubbing the eye, a blocked duct or allergies. Then clean and dry the area daily with saline and gauze and keep the fur short. Old stains won't wash out, but new fur will grow in lighter. Skip oral tear-stain products without a prescription, since some have contained antibiotics.

Is it normal for a puppy to have a lot of eye discharge?

A little crust is normal, but a puppy with heavy discharge, especially yellow or green in both eyes, should see a vet. In puppies who haven't finished their vaccines, infectious diseases like distemper need to be ruled out, along with eyelid problems that often show up in the first months of life.

Sources

Merck Veterinary Manual: disorders of the conjunctiva, cornea and tear (nasolacrimal) system in dogs.
American College of Veterinary Ophthalmologists (ACVO): owner information on dry eye and corneal ulcers.
World Small Animal Veterinary Association (WSAVA): canine vaccination guidelines.
American Animal Hospital Association (AAHA): canine vaccination guidelines.

This article is for information only and is not a substitute for a veterinary exam. If your dog gets worse, is in pain or shows warning signs, call your vet or an emergency animal hospital.