Cat Eye Discharge and Conjunctivitis: Causes, Safe Cleaning, and When to See the Vet

A little sleep crust in the corner of your cat's eye is normal. Squinting, a swollen pink eyelid, or a steady stream of yellow-green discharge is not. Conjunctivitis, inflammation of the thin membrane lining the eyelids and covering the white of the eye, is one of the most frequent feline eye problems, and in cats it is very often tied to infection.

What Normal Eye Discharge Looks Like

Healthy eyes make tears constantly, and a small amount of dried, brownish material in the inner corner is just tears mixed with dust and oil. It wipes away easily and comes back in small amounts. Flat-faced breeds such as Persians often have more tear staining because their tear ducts drain less efficiently.

Common Causes of Eye Discharge

• Feline herpesvirus (FHV-1): the most common cause of conjunctivitis in cats. Most cats are exposed as kittens, and the virus can flare up later during stress, illness or a change in routine.
• Chlamydia and Mycoplasma: bacteria that cause persistent, often one-sided conjunctivitis, frequently with swelling of the membrane.
• Upper respiratory infection: sneezing and runny eyes often come together, especially in shelters and multi-cat homes.
• Corneal ulcers or scratches: these cause squinting, watering and pain, and need prompt treatment.
• Allergies and irritants: pollen, dust, smoke or aerosol sprays can leave eyes red and watery.
• Blocked tear ducts: tears spill over the cheek instead of draining, often staining the fur.
• Foreign material: a grass seed, litter dust or a stray hair can irritate the eye.
• Deeper disease: uveitis and glaucoma can look like a red, weepy eye but are emergencies.

Reading the Discharge

The colour and amount offer clues, though only a vet can say what is behind them.

• Clear and watery: irritation, allergy, early viral infection, or a blocked duct.
• Thick yellow or green: usually points to a secondary bacterial infection.
• Dark brown or reddish crust: dried tears, or old blood; common in flat-faced breeds.
• One eye versus both: one eye suggests a local problem such as a scratch or foreign body, while both eyes together suggest infection or allergy.

Other Signs to Watch For

• Squinting or holding the eye shut
• Red or swollen eyelid tissue
• Third eyelid partly covering the eye
• Pawing or rubbing at the face
• Sneezing, nasal discharge or fever
• Cloudiness, a visible spot on the surface, or unequal pupils

A vet walks through the symptoms and treatment of feline conjunctivitis.

How to Clean Your Cat's Eyes Safely

Gentle cleaning is fine for mild, routine crust once your vet has ruled out anything serious. It is not a substitute for treatment.

1. Wash your hands, and wrap a fidgety cat loosely in a towel.
2. Use sterile, preservative-free saline made for eyes on a soft cotton pad. Avoid tap water, tea, soap or human eye drops.
3. Rest the damp pad on the crust for a few seconds to soften it.
4. Wipe from the inner corner outward, away from the eye.
5. Use a fresh pad for each eye, so infection cannot spread from one to the other.
6. Never touch the surface of the eye, and finish with a treat.

What the Vet May Do

Your vet will usually check the eye with a light and may apply a fluorescein stain, which glows where the cornea is damaged. They may also test tear production, measure eye pressure, or swab for infection. Treatment depends on the cause: antibiotic ointment for bacterial infection, antiviral medication for herpesvirus, lubricating drops, or treatment for an ulcer. Many cats also benefit from supportive care such as lysine in some vets' protocols, though the evidence for lysine is mixed.

Never use leftover drops, or any drop containing a steroid, unless your vet prescribes it. Steroids can make a herpes flare or a corneal ulcer much worse, and can even cost a cat its eye.

Why conjunctivitis keeps coming back in some cats.

When to See a Vet Straight Away

• Your cat is squinting hard or keeping an eye closed
• The surface of the eye looks cloudy, blue or has a visible spot
• The eye is bulging, very red, or the pupils differ in size
• There has been an injury, even a minor scratch
• Discharge is thick, green or bloody
• The problem has lasted more than a day or two, or keeps returning
• The cat is a kitten, or is also off food, lethargic or feverish

Eyes can deteriorate quickly. A corneal ulcer that is treated early often heals in days, while an untreated one can rupture.

Preventing Flare-Ups

• Keep vaccinations current, since the core vaccine covers herpesvirus and calicivirus and reduces how severe the disease is.
• Reduce stress with stable routines, hiding places and gradual introductions to new pets.
• Isolate a new or sick cat and wash hands between cats.
• Keep litter low-dust and avoid aerosols, smoke and strong fragrances near your cat.
• Gently wipe tear-prone breeds daily, as advised by your vet.

The Bottom Line

Mild crust that clears with a gentle wipe is usually harmless. Squinting, colour, redness or any change in the surface of the eye deserves a vet visit the same day. Because the right drops depend on the cause, guessing at home can make things worse.

This article is general information, not veterinary advice. If you are worried about your cat's eyes, contact your vet.