Cat Eye Discharge & Conjunctivitis: When It’s Nothing and When It’s Not

A little sleep in the corner of a cat's eye after a nap is normal. A cat squinting, pawing at its face, or waking up with an eyelid glued shut by crusted discharge is not — and it's one of the most common reasons cats end up at the vet. The tricky part is that mild, self-resolving irritation and a genuine infection that needs treatment look almost identical for the first day or two. Knowing what to watch for buys you the right amount of urgency: calm monitoring for some cases, a same-day vet visit for others.

What Normal Discharge Looks Like

Cats, like people, produce a small amount of clear or slightly tinted rheum overnight, more so in flat-faced breeds like Persians and exotic shorthairs whose short tear ducts drain less efficiently. A bit of dried, light-brown residue in the inner corner that wipes away easily, with a bright, open, comfortable-looking eye underneath, isn't cause for concern. What changes the picture is volume, colour, and behaviour: thick yellow or green discharge, an eye held shut, visible redness or swelling, or a cat pawing repeatedly at its face all point toward something that needs attention.

The Usual Suspects

• Feline herpesvirus (FHV-1). By far the most common cause of feline eye trouble. The large majority of cats are exposed as kittens and carry the virus for life; it lies dormant and flares during stress — a house move, a new pet, a trip to the cattery — producing watery, then thicker, discharge in one or both eyes, often alongside sneezing. Flare-ups usually settle within one to two weeks but tend to recur.
• Chlamydia felis. A bacterial infection that typically starts in one eye before spreading to the second within a few days. The discharge often turns yellow-green as it progresses. Unlike herpesvirus, it responds fully to a proper course of antibiotics and doesn't linger for life.
• Conjunctivitis from allergies or irritants. Dust, pollen, cigarette smoke, or a scratch from rough play can inflame the conjunctiva without any infection at all. The discharge tends to stay clear or slightly cloudy rather than turning colour, and both eyes are often affected evenly.
• A foreign body or corneal scratch. A single affected eye, held shut, with the cat clearly guarding it, points toward something physical — a grass seed, an eyelash rubbing the wrong way, or a scratch from another cat. These need a vet's fluorescent-stain exam to rule out a corneal ulcer, which can be serious if missed.
• Blocked tear ducts. Chronic, low-grade watery staining down one or both sides of the nose, without redness or squinting, is common in flat-faced breeds and some cats after a resolved infection left scarring in the tear duct. It's cosmetic rather than painful, though a vet visit is still worth it to confirm nothing else is going on.

A vet walks through what feline conjunctivitis looks like and how it's typically treated.

When It's an Emergency, Not a Wait-and-See

Most eye discharge is uncomfortable rather than dangerous, but a handful of signs mean same-day veterinary care rather than home monitoring:

• The eye is held completely shut, or the cat won't let you look at it at all
• You can see a cloudy patch, a visible scratch, or an odd bulge on the surface of the eye itself
• One pupil looks a different size or shape than the other
• The eye looks like it's bulging out of the socket, however slightly
• Discharge is accompanied by obvious pain — pawing, rubbing the face along furniture, or avoiding light
• A kitten with crusted-shut eyes, since untreated infection at that age carries a real risk of lasting eye damage

A corneal ulcer in particular can go from minor to sight-threatening within a couple of days if it's missed, which is why "wait a day and see" is the wrong call for a single red, weeping, tightly closed eye — that combination is worth a same-day exam even if the cat is otherwise acting normal.

A rundown of the specific signs that separate ordinary discharge from an infection worth a vet visit.

What You Can Safely Do at Home

• Wipe, don't rub. Use a fresh cotton pad or gauze square moistened with warm water for each eye — reusing the same pad on both risks spreading infection from one to the other. Wipe gently from the inner corner outward, and let crusted discharge soften for a minute before trying to remove it rather than pulling at dried debris.
• Don't reach for human eye drops. Products formulated for people, including many "natural" or preservative-free ones, aren't tested for feline eyes and some ingredients are actively unsafe for cats. Saline solution intended for contact lenses is a reasonable stopgap for a gentle rinse, but anything beyond that should come from a vet.
• Keep the rest of the household calm. Because herpesvirus flares are so often stress-triggered, reducing whatever's unsettled in the environment — a new pet introduction going too fast, a change in routine — helps as much as any treatment during a flare-up.
• Finish the full course if antibiotics are prescribed. Chlamydial conjunctivitis in particular looks better well before the infection is fully cleared; stopping early is the single biggest reason it comes back.

Multi-Cat Households

Both herpesvirus and chlamydia spread easily between cats sharing food bowls, bedding, and grooming sessions. If one cat in the home develops eye discharge, keep their bedding and bowls separate where practical, wash your hands between handling cats, and watch the others for early signs over the following one to two weeks. Vets often treat every cat in the household together when chlamydia is confirmed, since it moves through a multi-cat home quickly enough that treating one cat in isolation rarely holds.

The Bottom Line

A little clear residue that wipes away easily isn't worth a special trip. Thick or coloured discharge, a squinting or held-shut eye, or any sign the cat is genuinely bothered by it is worth a same-day look, especially in a kitten or if only one eye is affected with visible surface changes. Eye problems in cats are rarely life-threatening, but several of the common causes are time-sensitive in a way that back pain or a skipped meal usually isn't — the eye itself can be permanently damaged by a delay that would be harmless anywhere else on the body.