Dog pink eye, or conjunctivitis, shows up as noticeably red, swollen tissue around one or both eyes, often with discharge that can range from clear and watery to thick yellow or green. Your dog will likely squint, paw at the affected eye, or rub their face against furniture and carpet. If you’re looking at your dog right now wondering whether something is wrong with their eye, here’s what to look for and what each sign means.
The Key Visual Signs
The most obvious sign is redness. The tissue lining your dog’s eyelids and the whites of their eyes will look noticeably pink or red. This happens because blood vessels in the conjunctiva (the thin membrane covering the eye) dilate and increase blood flow, making the area look inflamed and irritated.
Swelling is the second thing you’ll notice. The conjunctival tissue puffs up with fluid, sometimes dramatically. In mild cases, the eyelid lining just looks a bit puffy. In more severe cases, the tissue can balloon outward enough that it’s visible even when your dog’s eye is open. The eye may look like it’s partially closing on its own.
Squinting and rubbing are behavioral signs that go hand in hand with the visible changes. Dogs with conjunctivitis feel itchy and uncomfortable, so they’ll blink excessively, hold the affected eye partially shut, or use their paws and nearby surfaces to scratch at it. This rubbing often makes things worse, increasing redness and swelling.
What the Discharge Tells You
The type of discharge coming from your dog’s eye is one of the most useful clues about what’s going on. Not all discharge means infection.
Clear or watery discharge is the mildest type. It can result from allergies, dust, wind, or a mild irritant getting into the eye. A small amount of clear or slightly reddish-brown crust in the corners of your dog’s eyes each morning is normal, similar to the “sleep” humans get. If the watery discharge is a bit heavier than usual but your dog’s eye isn’t red or painful, it’s reasonable to monitor for a day or two.
Yellow or green discharge is a different story. This color typically signals a bacterial component to the inflammation. The discharge may be thick, sticky, or crusty, sometimes matting the fur around the eye or sealing the eyelids shut after sleep. When you see yellow or green discharge combined with redness and obvious discomfort, your dog needs a veterinary exam promptly. The bacteria involved may be opportunistic, meaning they take advantage of tissue that’s already irritated rather than being the original cause of the problem.
Mucus-like discharge falls somewhere in between. It’s thicker than tears but not colored like pus. This can show up with dry eye, allergies, or early-stage infections before bacteria fully take hold.
One Eye or Both?
Whether one or both eyes are affected helps narrow down the cause. Pink eye in both eyes often points to allergies, a viral infection, or an environmental irritant like smoke, dust, or chemical fumes. When only one eye is affected, a foreign body (grass seed, dirt, a stray hair), a blocked tear duct, or dry eye are more likely culprits. Eyelid abnormalities that cause chronic irritation also tend to affect one eye more than the other, though they can involve both.
Common Causes Behind the Symptoms
Allergies and environmental irritants are among the most frequent causes of conjunctivitis in dogs. Pollen, mold, dust mites, household cleaners, and cigarette smoke can all trigger the redness and watery discharge that look like classic pink eye. Dogs with seasonal allergies often get conjunctivitis alongside itchy skin, sneezing, or ear infections.
Bacterial infections cause the yellow or green discharge most people associate with pink eye. These infections can start on their own or develop as a secondary problem after allergies, dry eye, or a scratch to the cornea weakens the eye’s natural defenses.
Dry eye, known clinically as keratoconjunctivitis sicca, happens when a dog’s tear glands don’t produce enough moisture. Without adequate tears to wash away debris and bacteria, the conjunctiva becomes chronically inflamed. Dogs with dry eye often have thick, stringy mucus discharge and dull-looking eyes.
Eyelid shape problems put certain breeds at higher risk for repeated bouts of conjunctivitis. Entropion (eyelids that roll inward) causes lashes to scrape against the eye surface constantly. Ectropion (eyelids that droop outward) exposes the inner lining to irritants. Research from the Royal Veterinary College found that eyelid conformation disorders were diagnosed in 15.5% of Shar-Peis, 9.6% of Chow Chows, 9.5% of Neapolitan Mastiffs, and 6.1% of Saint Bernards in a single study year. Spaniel breeds as a group had 2.5 times the risk of eyelid problems compared to crossbred dogs. English Bulldogs and Clumber Spaniels also ranked high on the list.
Conditions That Look Like Pink Eye but Aren’t
A red, painful eye doesn’t always mean conjunctivitis. Two serious conditions, glaucoma and uveitis, can mimic pink eye in the early stages but require urgent treatment to prevent vision loss.
Glaucoma causes a sudden increase in pressure inside the eye. The eye looks red and congested, and your dog will be in obvious pain. The key visual difference is the pupil: in glaucoma, the pupil is typically dilated (large and wide) and doesn’t respond normally to light. The cornea may also look hazy or cloudy, almost like fogged glass. Glaucoma is an emergency.
Uveitis is inflammation inside the eye itself, not just the outer membrane. Dogs with uveitis are sensitive to light and may avoid bright rooms. Their pupil is typically constricted (small and tight), the opposite of glaucoma. You might notice cloudiness in the front chamber of the eye or a change in iris color. Reduced appetite and lethargy sometimes accompany it.
If your dog’s eye is red but you also notice a cloudy cornea, an unusually large or small pupil, or the eye appears to be bulging, those are signs of something more serious than simple pink eye.
What Happens at the Vet
A veterinary exam for suspected pink eye is straightforward and quick. The vet will examine the eye’s surface, check for foreign bodies under the eyelids, and assess tear production. One common test involves placing a small strip of orange dye on the eye’s surface. This fluorescein stain highlights any scratches or ulcers on the cornea by turning them bright green under ultraviolet light. It’s painless and takes seconds, but it’s important because a corneal ulcer changes the treatment plan entirely (certain anti-inflammatory drops can make ulcers worse).
Treatment depends on the cause. Bacterial conjunctivitis is typically treated with antibiotic eye drops or ointment applied several times a day for one to two weeks. Allergic conjunctivitis may call for anti-inflammatory drops and identifying the allergen. Dry eye requires long-term tear-stimulating medication. Eyelid problems in predisposed breeds sometimes need surgical correction to prevent lifelong irritation.
Most straightforward cases of bacterial conjunctivitis improve noticeably within a few days of starting treatment, with full resolution in one to two weeks. Allergic conjunctivitis can clear up quickly once the trigger is removed but tends to recur seasonally. Dry eye and structural eyelid issues require ongoing management.
Safe Home Care for Mild Cases
If your dog’s eye is mildly red with clear, watery discharge and no obvious pain, you can gently flush the eye with sterile saline eye wash, available over the counter at most pharmacies. Use it to rinse away debris, dust, or dried discharge from around the eye. You can do this several times a day.
One important warning from the American College of Veterinary Ophthalmologists: do not use contact lens solution on your dog’s eyes. Contact lens solutions contain enzymes designed to clean lenses that are harmful to the eye’s surface.
Use a warm, damp cloth to soften and wipe away any crusted discharge around the eyelids, working gently from the inner corner outward. Keep your dog from rubbing or scratching at the eye. A cone collar can help if they won’t leave it alone. Never apply human eye drops containing redness relievers or antihistamines unless specifically directed by your vet, as some ingredients that are safe for people can be toxic to dogs.
If symptoms don’t improve within a day or two, or if you see yellow or green discharge at any point, the home care window has closed and your dog needs professional treatment.