Red or runny eyes in cats

A cat with a red, weepy, or squinted eye should be seen by a veterinarian promptly, ideally the same day, because the feline eye can go from mildly irritated to seriously damaged in a matter of hours. Redness, watering, and pawing usually mean the surface of the eye or the tissue around it is inflamed, and while the most common cause in cats is a treatable infection, the same signs can also point to a painful corneal ulcer or rising pressure inside the eye that threatens sight. When you cannot tell the difference at home, the safest assumption is that the eye needs professional attention quickly.

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What is actually happening behind a red or runny eye

The visible white of a cat's eye and the pink lining inside the lids are covered by a thin, blood-rich membrane called the conjunctiva. When something irritates or infects the eye, those tiny vessels swell and the eye looks pink or red. Tears are the eye's built-in defense, so the same irritation that causes redness usually triggers extra watering, and a cat that is uncomfortable will squint, blink hard, or rub its face against furniture. In other words, redness, discharge, and squinting are not three separate problems. They are the eye's shared response to inflammation, and the job of a vet visit is to work out what set that inflammation off.

The tricky part is that very different conditions produce very similar-looking eyes. A simple case of conjunctivitis and a deep corneal ulcer can both give you a red, runny, half-closed eye, yet one may clear up with drops while the other can perforate and cost the eye if it is missed. Cats also tend to underplay discomfort, so a cat that is still eating and moving around normally can nonetheless be in real pain. This is exactly why home guesswork is risky with eyes, and why the guidance for cats leans toward seeing a vet sooner rather than later.

Why feline herpesvirus is so often behind it

In cats, the single most common driver of red, weepy eyes is feline herpesvirus, the main cause of the upper respiratory disease often called cat flu. A very large share of cats are exposed to this virus early in life, and once infected they carry it for good. The virus inflames the conjunctiva and can also damage the cornea, which is why herpes flare-ups so often show up as a red, runny eye paired with sneezing and nasal discharge. A cat may look completely healthy for months and then break out with sore eyes again, especially after a stressful event.

Stress is the key trigger to understand. A house move, a new pet, boarding, or even a change in routine can reactivate the virus, so many owners notice their cat's eyes flaring up at predictable stressful moments. Kittens, cats in multi-cat homes, and shelter cats are especially prone to these episodes. Because herpes-related inflammation weakens the eye's surface, it also opens the door to secondary bacterial infection, which is what turns a watery eye into one with thicker, colored eye discharge. None of this means you should treat at home on your own, because the very medications that help a bacterial flare can be dangerous if a herpes ulcer is present.

How vets pinpoint the cause in cats

A vet cannot tell which of these conditions is present just by looking, so an eye exam follows a fairly set routine. One of the first and most important steps is a fluorescein stain, where a harmless orange-green dye is applied to the eye and any scratch or ulcer on the cornea lights up. Your vet will usually also measure the pressure inside the eye to rule out glaucoma, and check tear production to see whether dry eye is contributing. They will examine the eye closely for a foreign body such as a grass seed or grit tucked behind the third eyelid, and look at the overall pattern of signs to judge whether a herpes flare, an allergy, or an injury is the more likely story.

What to expect at the vet visit

Once the exam has identified the problem, treatment is aimed at the specific cause rather than the redness itself. For conjunctivitis and secondary bacterial infection, your vet may prescribe antibiotic eye drops or ointment. If a corneal ulcer is found, treatment focuses on pain relief, protecting the surface while it heals, and preventing infection, and your vet will recheck the stain to confirm the ulcer is closing. When feline herpesvirus is the underlying driver, antiviral medication and supportive care may be added, and your vet may talk about long-term management because the virus tends to return. In serious or stubborn cases, especially anything involving deep ulcers or high eye pressure, your vet may refer you to a veterinary eye specialist.

Recovery for a straightforward infection is often quick, with visible improvement within a few days of starting the right medication, though a full course should always be finished even if the eye looks better. Corneal ulcers take longer and usually need one or more rechecks to be sure they have healed. A recovery collar is one of the most useful tools your vet will send home, because a single afternoon of rubbing can undo days of healing. Costs vary with what is found, from a simple consultation and a course of drops for mild conjunctivitis, up to specialist care for a complicated ulcer, so it is worth asking for a clear estimate and a plan at the visit.

How to help at home safely

Safe home care is about comfort and cleanliness while you arrange the appointment, not about trying to cure the eye yourself. You can gently wipe away discharge with a clean, damp cloth or cotton pad, using a separate wipe for each eye so you do not carry infection from one side to the other, and always wiping from the inner corner outward. Keep your cat from rubbing or pawing at the eye, discourage face-rubbing on rough surfaces, and reduce stress at home, since stress can prolong a herpes flare. Keep an eye on the bigger picture too, because a cat that also stops eating during a flare, which you can read more about on our guide to a cat that is not eating, may need extra support and a call to your vet.

Lowering the risk of future flare-ups

You cannot clear feline herpesvirus from a cat that already carries it, but you can make flare-ups less frequent and less severe. Because stress is the main trigger, the most useful prevention is a stable, low-stress home: predictable routines, enough resources such as litter trays and hiding spots in multi-cat households, and gentle introductions when circumstances change. Keeping up with the core vaccines your vet recommends helps reduce the severity of respiratory and eye disease, and prompt treatment of the first sign of a flare tends to shorten it. For cats prone to trauma or foreign bodies, limiting unsupervised time in long grass and keeping the face free of matted fur around the eyes can help. If your cat has recurring bouts, ask your vet whether a longer-term management plan makes sense for your cat.

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You can also read about common feline medications in the Webvet Rx Database, though any drug for your cat's eyes should be chosen and dosed only by your own veterinarian.

When red or runny eyes become an emergency

Some eye signs cannot wait even for a same-day appointment. A cloudy, bulging, or visibly injured eye, a sudden and severe onset of pain, a cat that cannot open the eye at all, or any suspicion that vision has changed all warrant contacting a veterinarian or emergency clinic immediately. The reason for urgency is simple: conditions like a deep corneal ulcer or acute glaucoma can permanently destroy sight within hours, and pain in cats is often more advanced than it looks because they instinctively mask it. When in doubt, err on the side of being seen. An eye that turns out to be a minor irritation is a small inconvenience, whereas a missed emergency can cost your cat an eye. If you are ever unsure how serious your cat's eye looks, a phone call to your vet for guidance is always the right first move.