Dog Conjunctivitis: Pink Eye, Discharge & When to Worry

Bottom line: Conjunctivitis is inflammation of the conjunctiva — the pink tissue lining the eyelid and eyeball — and in dogs it shows up as redness, squinting, and a watery or colored discharge. Most cases need a vet to pin down the cause, because an infection, an allergen, and a scratched cornea are treated very differently.

What conjunctivitis actually is

The conjunctiva is the moist, pink membrane you see if you gently lift a dog's lower lid. When it gets irritated, it swells and reddens, the eye waters, and a film of mucus or pus can form. It is the dog equivalent of pink eye in people, but the causes and risks are not the same — and dogs cannot tell you it itches.

Conjunctivitis is a sign, not a disease. Treating only the redness without finding the trigger is like mopping the floor while the tap is still running.

Common causes in dogs

1. Allergies — seasonal pollen, dust, or food sensitivities make eyes weep and itch, often with clear discharge and no pain.

2. Bacterial or viral infection — produces thicker yellow-green pus and often affects one eye first, then the other.

3. Irritants — smoke, shampoo, dust, or wind-blown grit inflame the eye on contact.

4. Anatomical traits — flat-faced breeds (Pugs, Bulldogs, Shih Tzus) have shallow sockets and lids that do not close fully, so the eye dries and irritates easily.

5. Something behind it — a corneal ulcer, a foreign body, or even glaucoma can masquerade as simple conjunctivitis. That is why guessing at home is risky.

Our eye care guide covers daily habits that lower the odds of irritation in the first place.

Symptoms you can spot at home

• Redness of the pink tissue around the eye.
• Squinting or holding the eye partially closed.
• Discharge that is clear, white, or yellow-green and may crust the lashes shut overnight.
• Pawing or rubbing at the face.
• Light sensitivity — the dog ducks away from bright rooms.

Clear, watery, both-eyes, no-pain weeping leans allergic. One eye, thick green pus, and squinting leans infection or injury. But these are clues, not a diagnosis.

Breed matters too: flat-faced dogs and those with prominent eyes (Pugs, Shih Tzus, Boston Terriers) get conjunctivitis more often and more seriously because their eyes sit exposed and their lids do not close fully at night. For them, even mild redness is worth a sooner check.

What you should NOT do at home

• Do not use human eye drops unless your vet specifically says so. Many contain ingredients that are unsafe for dogs, and steroid drops can worsen an undiagnosed ulcer badly.
• Do not wait weeks hoping it clears, especially if only one eye is affected or the dog is in obvious discomfort.
• Do not try to flush a suspected ulcer or remove a foreign body yourself — you can scratch the cornea further.

The safest home step is a clean, warm, damp cloth to gently wipe away crust, from the inner corner outward, once, then discard. That is comfort only — not treatment.

What a vet visit actually involves

Expect a quick, usually painless work-up. The vet will hold the lids open, check each eye with a light, and very often apply a fluorescein stain — a harmless orange dye that glows under a blue light to reveal scratches on the cornea. They may measure tear production with a tiny paper strip and check eye pressure to rule out glaucoma. Based on that, treatment is targeted: antibiotic drops for bacterial infection, antihistamine or allergy management for irritant cases, or lubricants for dryness. You will leave with a clear plan rather than a guess.

When to see a vet

This is general information, not veterinary advice. Eye problems can escalate fast, so when in doubt, the clinic is the right call.

Protecting eye health long-term

• Wipe faces of tear-stain-prone and flat-faced breeds daily with a vet-approved pad.
• Trim bangs that poke the eye in long-haired dogs.
• Rinse after swimming in chlorinated or salty water.
• Keep eye care products breed-appropriate, and never assume redness is only cosmetic.

Catching conjunctivitis early and getting the right cause treated is the difference between a few days of drops and a damaged eye. When the eye looks wrong, let the professionals look.

Sources: VCA Animal Hospitals — Conjunctivitis in Dogs; AAHA — Eye Care Guidelines for Dogs and Cats; Cornell University College of Veterinary Medicine — Canine Eye Health.

This article is educational and not a substitute for veterinary advice. If your pet shows pain, sudden behavior change, or emergency signs, contact a licensed veterinarian.