Conjunctivitis in Cats: Causes & Treatment
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Conjunctivitis — inflammation of the pink tissue lining the eye and eyelids — is the most common eye problem in cats. It causes red, swollen, watery or squinting eyes, often with discharge. In cats it's frequently linked to infections like feline herpesvirus. Some cases are mild, but eye problems can worsen quickly, so a cat with a painful, squinting or cloudy eye should be seen by a vet.
When an eye problem is urgent
See a vet promptly if your cat has a cloudy eye, a visible ulcer or wound, a tightly held-shut or clearly painful eye, sudden swelling, or is pawing hard at the eye. Eye conditions can progress fast, and what looks like simple conjunctivitis can involve the cornea. When the eye itself looks damaged or your cat is in pain, don't wait.
Milder cases — a bit of redness and watering in a comfortable, bright-eyed cat — can often be checked at your vet's next available appointment, but any eye that's getting worse deserves a same-day call.
What causes conjunctivitis in cats
Unlike in dogs, infections are the leading cause in cats:
- Feline herpesvirus (FHV-1) — a very common cause, often alongside upper respiratory signs, and prone to recurring with stress.
- Chlamydia felis and Mycoplasma — bacterial causes that frequently affect the eyes.
- Calicivirus and other respiratory viruses.
- Irritants and allergies — dust, smoke or foreign material.
- Injury or a scratch to the eye surface.
Because herpesvirus is so common in cats, conjunctivitis often comes and goes over a cat's life, flaring at stressful times.
Signs to look for
Conjunctivitis can affect one or both eyes:
- Redness and swelling of the pink tissue around the eye
- Watery, mucousy or crusty discharge
- Squinting or blinking a lot, or holding the eye partly closed
- Pawing or rubbing at the eye
- The third eyelid showing across part of the eye
- Sneezing or nasal discharge if a respiratory infection is involved
One-eye involvement often points to irritation or injury, while both eyes together more often suggests an infection or allergy — but a vet exam is the reliable way to tell.
How it's diagnosed and treated
Your vet examines the eye, usually checks tear production and stains the surface with a dye to look for corneal ulcers, and may test for specific infections. Treatment targets the cause:
| Cause | Typical treatment |
|---|---|
| Bacterial (Chlamydia, Mycoplasma) | Prescription antibiotic eye medication. |
| Herpesvirus | Supportive care, sometimes antiviral eye medication, and reducing stress. |
| Irritant or foreign material | Flushing the eye and removing the source. |
| Corneal ulcer | Specific medication and close monitoring — not just conjunctivitis treatment. |
Practical take: Never use a leftover or human eye medication on your cat. Some human products contain steroids that can seriously worsen a corneal ulcer. Always get the right prescription for the cause.
Recurrence and monitoring
Because herpesvirus-related conjunctivitis tends to recur, many cats have occasional flare-ups, often tied to stress. Keeping a simple log of which eye is affected, when flares happen, and what preceded them helps you and your vet identify triggers and decide whether a recurring bout is routine or needs a deeper look. If an eye ever changes quickly or looks painful, treat it as a fresh problem rather than assuming it's the same old flare.
Track eye flare-ups to find the triggers
Tavi lets you log symptoms, medications and vet visits and view them over time, so recurring eye trouble becomes a pattern you and your vet can actually act on. Free for your first pet.
Frequently asked questions
What does conjunctivitis look like in cats?
The eye looks red and swollen, often watery or with mucousy discharge, and the cat may squint, blink a lot or hold the eye partly closed. One or both eyes can be affected, and the third eyelid may show.
Is cat conjunctivitis contagious?
The infectious causes, like feline herpesvirus and Chlamydia felis, are contagious to other cats. They are not generally contagious to humans or dogs, but affected cats should be kept away from other cats until treated.
Can I use human eye drops on my cat's eye?
No, not without veterinary guidance. Some human eye products contain steroids that can seriously worsen a corneal ulcer, which can hide behind what looks like simple conjunctivitis. Always get the correct prescription for the cause.
Will cat conjunctivitis go away on its own?
Mild irritant cases sometimes settle, but infectious conjunctivitis usually needs treatment, and untreated eye problems can worsen. Because a corneal ulcer can look similar and is serious, it's safest to have a squinting or worsening eye checked.
Why does my cat's conjunctivitis keep coming back?
Recurrent conjunctivitis in cats is often due to feline herpesvirus, which many cats carry for life and which flares at stressful times. Reducing stress and treating flares promptly helps, and tracking triggers makes recurrences easier to manage.
Tavi's guides are informational and not a substitute for professional veterinary advice, diagnosis or treatment. When in doubt, call your veterinarian. Sources: Cornell University Feline Health Center; American College of Veterinary Ophthalmologists; VCA Animal Hospitals; Merck Veterinary Manual