If your cat has a red, watery or irritated eye, conjunctivitis is one possible cause. Conjunctivitis is inflammation of the conjunctiva (a thin membrane that lines the inside of the eyelids and covers the white part of the eye) and is a sign that something is irritating or affecting the eye.
Conjunctivitis can be caused by many different things, from infections and allergies to injuries and deeper, more serious eye conditions. Because eye problems in pets can get worse very quickly, it’s essential to book an appointment with your vet as soon as you notice any changes to your cat’s eyes.
What are the signs of conjunctivitis in cats?
Common signs of conjunctivitis in cats include:
- Redness and swelling around the eye(s) or inside the eyelids
- Watery eyes or excessive tear production
- Sticky discharge (yellow, green, or white) collecting in the corners
- Swollen, puffy eyelids
- Blinking more than usual, squinting, or holding the eye(s) completely closed
- Pawing at the eye(s) or rubbing their face against carpets and furniture
- Cloudiness or a bluish haze across the front surface of the eye
What causes conjunctivitis in cats?
Conjunctivitis in cats can be triggered by a wide range of issues, including:
Cat flu (feline herpesvirus):
One of the most common causes of feline conjunctivitis is Feline Herpesvirus (FHV-1) — one of the viruses responsible for cat flu. Many cats become infected as kittens and carry the herpesvirus for life. Although they may remain perfectly healthy for long periods, stress, illness, or changes in routine can cause the virus to reactivate, leading to recurring flare-ups of conjunctivitis.
Cats with cat flu may also show:
- Sneezing and a runny nose
- Lethargy and fever
- Painful corneal ulcers (open sores on the clear surface of the eye)
Bacterial infections:
While bacterial eye infections can happen on their own, they usually crop up as a secondary issue — taking advantage when the eye is already weakened by something else, like a virus or injury.
Foreign bodies and injuries:
Grass seeds, grit, dust, or small pieces of debris can become trapped beneath the eyelids, causing severe irritation. Scratches from branches or outdoor cat fights can also damage the eye. Even a minor surface scratch on the eye is extremely painful and vulnerable to infection.
Allergies:
Cats can occasionally develop conjunctivitis from environmental allergens like pollen, dust mites, moulds, or household sprays and cleaning products.
Eyelid problems:
Conditions such as entropion (where the eyelid rolls inwards towards the eye) or ectropion (where the eyelid droops outwards) cause constant irritation to the surface of the eye. Flat-faced (brachycephalic) breeds like Persians tend to be most affected, though eyelid problems are generally less common in cats than in dogs.
Eyelash problems:
Extra or misplaced eyelashes growing in the wrong direction (like distichiasis/ectopic cilia) can constantly rub against the delicate surface of the eye, causing weeping and inflammation.
Dry eye (keratoconjunctivitis sicca):
Dry eye — caused by poor tear production — is relatively uncommon in cats, but it can occur following severe viral infections or immune-mediated diseases. Without enough tears to lubricate the surface, cats experience repeated, painful bouts of conjunctivitis with thick discharge.
Other serious eye diseases
Some serious eye conditions can threaten your cat’s eyesight and may initially look like simple conjunctivitis. These include:
- Glaucoma: A painful buildup of pressure inside the eye
- Uveitis: Painful inflammation deep inside the eyeball
- Lens problems: Issues with the lens inside the eye moving out of place
How is conjunctivitis diagnosed and treated?
Because conjunctivitis can be caused by so many different things, the right treatment will depend on what exactly is causing the problem. To begin with, your vet will carefully examine your cat’s eyes to identify the problem. They may also need to carry out some quick tests:
- Green dye test (fluorescein stain): A special dye shows up any hidden scratches or sore spots on the front of the eye
- Tear test: Uses tiny paper strips to see if your cat is making enough tears
- Eye pressure test: Checks the pressure inside the eye to rule out conditions like glaucoma
- Swabs: If the problem keeps coming back, your vet may take a quick swab to test for specific viruses or bacteria
Treating the Eye:
Once your vet knows what’s going on, they will prescribe an appropriate treatment for your cat. This might include:
- Medicated eye drops or ointments: Antibiotics for bacterial infections, antiviral medication for cat flu, or perhaps anti-inflammatory drops to reduce swelling
⚠️ Important: Never use leftover eye drops or human medications. Using the wrong drops, especially on a scratched eye, can cause severe, permanent damage.
- Lubricating eye gels: False tears that keep the eye moist, clean, and comfortable
- Surgery: If something like an extra eyelash or a turned-in eyelid is constantly rubbing against the eye, a small operation may be required to fix it
What if it doesn’t get better?
If your cat’s symptoms don’t improve quickly with treatment, have them checked again by your vet. If your cat suffers from regular flare-ups of conjunctivitis, it suggests an underlying problem that needs investigation.
When to contact your vet
Never wait and see – eye problems can worsen quickly, so it is always best to contact your vet as soon as you notice signs of a problem.
Contact your vet promptly if your cat has:
- A red, swollen, or cloudy eye
- Yellow, green, or sticky discharge
- Squinting, rubbing, or blinking constantly
- Repeated bouts of conjunctivitis
Emergency: Go to your vet or out-of-hours clinic right away if your cat:
- Cannot open their eye at all
- Is showing signs of severe pain, particularly if they are hiding or unusually withdrawn
- Has a bulging eye, blood in the eye, or a visible injury
- Suddenly loses their sight or bumps into things