Conjunctivitis in Cats: Red, Runny Eyes and How They Are Treated

By Tailwisp Editorial TeamUpdated October 20, 20264 min read

Red, weepy, squinting eyes are one of the most common reasons cats see the vet. Conjunctivitis, often called pink eye, is common, and while many cases are mild, eye problems can quickly become serious. Prompt checks protect your cat's vision.

What is conjunctivitis?

The conjunctiva is the thin, moist membrane that lines the eyelids and covers the white of the eye. When it is inflamed, it becomes red and swollen, and the eye produces more discharge. It can affect one eye or both.

Causes

• Feline herpesvirus (FHV-1). The leading cause, especially in kittens and shelter cats. Once infected, a cat carries the virus for life, and stress can trigger flare-ups. See upper respiratory infections in cats.
• Chlamydia felis. A bacterium that causes persistent conjunctivitis, often with swelling.
• Other bacteria, such as Mycoplasma.
• Allergies. Dust, pollen and other triggers. See cat skin allergies.
• Foreign bodies, such as grass seeds or dust.
• Injury, including scratches in fights.
• Dry eye.
• Blocked tear ducts.
• Eyelid abnormalities, such as entropion, where the lid rolls in.
• Other eye disease, such as glaucoma or uveitis. See cat eye problems and cat glaucoma.

Signs

• Red or pink eye tissue.
• Swelling of the lids and the tissue.
• Watery, cloudy, yellow or green discharge.
• Squinting, or keeping the eye closed.
• Pawing or rubbing the eye.
• Third eyelid showing.
• Sneezing and nasal discharge, in cases linked to respiratory infection.
• Cloudiness or color change in the eye, which needs urgent care.

Discharge colors

Clear and watery discharge can come from viruses, allergies or irritation. Yellow, green or thick discharge often suggests bacterial involvement. These are only guides, and the vet's exam matters most.

Why not wait and see

Eyes can deteriorate within hours. Corneal ulcers, glaucoma and uveitis can cause pain and blindness, and require different treatment. Do not use leftover medication, or human eye drops, because some contain steroids, which can make ulcers worse.

Diagnosis

The vet examines the eyes, uses a dye to check for ulcers, measures tear production and eye pressure, and may take swabs for PCR tests for herpesvirus and chlamydia.

Treatment

• Antibiotic drops or ointment, such as for chlamydia, usually for several weeks.
• Antivirals, for herpesvirus, in some cases.
• Pain relief and lubricants.
• Treating the cause, such as removing foreign bodies or correcting eyelids.
• L-lysine, sometimes used for herpesvirus, though evidence is limited. Ask your vet.
• Treat in-contact cats, in cases of chlamydia.

See how to give cat eye drops.

Home care

• Gently wipe discharge with a clean, damp cotton pad, one wipe for each eye.
• Wash your hands between cats.
• Keep the cat indoors.
• Use an Elizabethan collar if the cat rubs the eye.
• Reduce stress. See signs of stress in cats.
• Keep vaccinations current. See cat vaccination schedule.

Kittens

Kittens commonly have eye infections. See kitten sneezing and eye discharge.

Herpesvirus flare-ups

Once a cat is infected with feline herpesvirus, the virus stays in the body, and signs may return during stress, illness or changes at home. Typical signs are red, runny eyes and sneezing. Flare-ups often settle in a week or two, but some cats need antiviral treatment or lubricants. Long-term lysine supplements are sometimes suggested, though studies have not shown clear benefit, so ask your vet. Keep stress low, and keep vaccinations current. Vaccines do not prevent infection, but they reduce the severity.

Chlamydia in multi-cat homes

Chlamydia spreads by close contact. If one cat in a home is diagnosed, vets often advise treating all in-contact cats for several weeks, since the infection can persist. Wash hands and bedding, and follow the full course of antibiotics, usually doxycycline. Chlamydia is rarely passed to people, but people with weakened immune systems should take extra care and speak to their doctor.

Chronic eye disease

If eye problems keep returning, your vet may recommend a referral to a veterinary ophthalmologist. Chronic herpesvirus can cause corneal scarring, ulcers and a condition called symblepharon, where the eyelid sticks to the eye. Early care protects vision.

Tracking progress at home

Take a photo of the eyes each day, so that you can see whether redness and discharge are fading. Note whether the cat eats, plays and squints less. If the eyes look worse after a few days of treatment, or the cat begins to hold one eye shut, call the vet again, since the diagnosis or treatment may need to change.

When to see a vet

See a vet the same day if the eye is red, swollen, cloudy or kept shut. Use the US vet directory to find a clinic.

This article is general educational information, not veterinary advice. Every cat is different. If your cat is unwell, or you are unsure about a symptom, diet change or medication, contact your veterinarian.