Dog Red Eyes: Common Causes and When to See a Vet

What it usually means

The most common cause is conjunctivitis, inflammation of the membrane that lines the eyelids and covers the white of the eye. In dogs it is often triggered by allergies to pollen, dust, or grass, by irritants such as smoke, wind, or shampoo, or by bacterial or viral infection. When both eyes are red, allergies or infection are more likely.

When only one eye is red, think of something local: a grass seed or speck of dirt under the lid, a scratch on the surface of the eye, an eyelash growing in the wrong direction, or an eyelid that rolls inward and rubs. Dry eye, where the eye stops making enough tears, also causes redness and thick discharge, mostly in middle-aged and older dogs.

Signs that come with red eyes

Look for squinting, blinking more than usual, holding an eye closed, pawing or rubbing the face, swollen eyelids, the third eyelid showing across the inner corner, and discharge that may be clear, white, yellow, or green. A dog who avoids bright light, or who rubs one eye along the carpet, is usually in discomfort.

A bright red spot on the white of the eye can be a burst blood vessel, which may follow coughing, straining, or a knock, and often fades by itself, though a vet should check that nothing deeper has changed. A round, red swelling in the inner corner is often a prolapsed tear gland, known as cherry eye, which needs a vet but is not usually an emergency.

When to call your vet today

Call your vet the same day if your dog is squinting or holding an eye shut, if the redness lasts more than a day, or if there is yellow or green discharge, swelling, or a change in how the eye looks. Eye problems can go from mild to serious quickly, and early treatment is usually simpler and more successful.

Also call if your dog keeps getting red, gooey eyes, or if a flat-faced breed such as a Pug, Shih Tzu, or Boston Terrier has any eye problem at all. Their prominent eyes are more easily injured and dry out more readily.

When it's an emergency

Go to an emergency vet now if the eye looks cloudy or bluish, if the eye seems larger than the other or bulges, if one pupil is much bigger than the other, or if your dog is in obvious pain or suddenly seems unable to see. These can be signs of glaucoma, a deep ulcer, or inflammation inside the eye, and sight can be lost within hours to days.

Any injury to the eye, such as a cat scratch, a stick, or a chemical splash, also needs care right away. If a chemical has gotten in the eye, gently flush it with plenty of lukewarm water or sterile saline while someone calls the vet, then go.

What you can safely do at home

Gently wipe away discharge from around the eye with a soft cloth or cotton pad dampened with sterile saline, working from the inner corner outward, and use a fresh piece for each eye. Stop your dog from rubbing by distracting them, and use a cone if your vet suggests one.

Do not use human eye drops, leftover medicine from another pet or a previous problem, or home remedies such as tea, vinegar, or essential oils. Some eye medicines that help one condition can seriously worsen another, such as an ulcer, so drops must be chosen by a vet after an examination.

What the vet will likely check

Your vet will look closely at the eyelids, lashes, and surface of the eye, and usually put a harmless orange stain on the eye to show any scratch or ulcer. A tear test measures whether the eye makes enough tears, and a pressure reading checks for glaucoma.

Depending on what they find, treatment may include eye drops or ointment, removal of a foreign object, treatment for allergies, or surgery for eyelid or tear gland problems. Some conditions, such as dry eye, need lifelong treatment, and your vet will plan rechecks to make sure the eye is healing.

Preventing eye problems

Keep long hair trimmed away from the eyes, rinse your dog's face after walks through long grass or dusty areas, and keep your dog's head inside the car rather than out of the window. Protect the eyes during baths by keeping shampoo away from the face.

If your dog has allergies, managing them with your vet also helps the eyes. Check your dog's eyes as part of your weekly routine: bright, clear, and open with no squinting is what you want to see.

This page is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your pet.