Feline conjunctivitis is usually treated with antibiotic eye drops or ointment applied three to four times daily for two to three weeks. In most cases, conjunctivitis in cats will actually resolve on its own without medication, but treatment speeds healing and prevents complications. The right approach depends on whether the cause is viral, bacterial, or something else entirely, so a vet visit is the best starting point.
What Causes Conjunctivitis in Cats
The most common culprit is feline herpesvirus (FHV-1), which the majority of cats are exposed to at some point in their lives. Once a cat is infected, the virus stays in the body permanently and can reactivate during periods of stress, illness, or immune suppression. Flare-ups cause red, watery, or goopy eyes that can recur throughout the cat’s life.
Bacterial infections, particularly from organisms like Chlamydia felis and Mycoplasma, are the other major infectious cause. These tend to produce thicker, yellow-green discharge and sometimes affect one eye before spreading to both. Cats can also develop conjunctivitis from allergens, dust, irritants, or a foreign body stuck under the eyelid.
What a Vet Visit Involves
Your vet will look at the eye under magnification and typically apply a fluorescein stain, a harmless orange dye dropped onto the eye’s surface. Healthy outer tissue repels the dye, but if there’s a corneal ulcer (a scratch or erosion on the surface of the eye), the dye soaks in and glows green under blue light. This step matters because certain medications, especially anything containing steroids, can make a corneal ulcer dramatically worse.
Beyond the stain test, some vets will take a swab to identify the specific pathogen involved, particularly if the infection keeps coming back or doesn’t respond to initial treatment. Knowing whether herpesvirus or a bacterium is driving the problem changes the treatment plan.
Antibiotic Treatment for Bacterial Cases
For bacterial conjunctivitis, vets typically prescribe a topical antibiotic ointment. You’ll apply a small strip (about a quarter inch) directly into the affected eye two to four times per day. Treatment usually lasts two to three weeks, and your vet will likely ask you to continue for a few days after the visible signs clear up to make sure the infection is fully gone.
It can feel awkward applying ointment to a cat’s eye at first. The trick is to gently pull the lower lid down with one hand, squeeze the strip of ointment along the inside of the lid, then let the cat blink to spread it across the eye. Having a second person hold the cat, or wrapping the cat snugly in a towel, makes the process much easier.
Treating Viral Conjunctivitis
When herpesvirus is the underlying cause, antibiotics won’t address the virus itself, though vets often prescribe them anyway to prevent secondary bacterial infections from taking hold on already-irritated tissue. The primary treatment for viral cases is an antiviral medication.
Oral antiviral tablets are the most common option for herpesvirus-related eye disease in cats, given every 8 to 12 hours until about a week after symptoms resolve. Topical antiviral eye drops also exist, but many of them require frequent application (every few hours in the early days), which can be difficult for cat owners to maintain. Your vet will choose based on the severity of the infection and how cooperative your cat is with eye drops.
The important thing to understand about herpesvirus is that treatment clears the active infection from the eye’s surface and lets it heal, but it doesn’t eliminate the virus from the body. Future flare-ups are possible, especially when the cat is stressed. Minimizing stress through stable routines, avoiding overcrowding, and keeping the cat’s overall health strong can reduce how often episodes return.
What You Can Do at Home
Gentle cleaning is the most helpful thing you can do between medication doses. Use plain sterile saline solution (the kind sold for wound irrigation, not contact lens cleaning solution) on a soft cotton ball or gauze pad. Wipe from the inner corner of the eye outward, using a fresh piece for each eye to avoid spreading infection between them. This removes crusty discharge that can seal the eyelids shut and cause further irritation.
Do not use human eye drops, contact lens solutions labeled “enzymatic” or “cleaning,” or any leftover medications from a previous pet or previous illness unless your vet specifically tells you to. Some human eye drops contain ingredients that are toxic to cats, and steroid-containing drops can cause serious damage if a corneal ulcer is present.
L-Lysine Does Not Work
You’ll find L-lysine supplements marketed heavily for cats with herpesvirus-related eye problems. The theory was that lysine might lower levels of another amino acid (arginine) that the virus needs to replicate. A systematic review of all available evidence found this isn’t what happens. Lysine does not antagonize arginine in cats, has no effect on herpesvirus replication, and showed no benefit in clinical trials. Some studies actually reported increased infection frequency and more severe disease in cats receiving lysine. The researchers recommended an immediate stop to lysine supplementation based on the complete lack of evidence for its use.
If your cat is already taking lysine treats or powder, stopping won’t cause any harm.
How Long Recovery Takes
Most straightforward cases of conjunctivitis clear up within two to three weeks with treatment. You should see improvement in the amount of discharge and redness within the first week. If your cat’s eyes look worse after a few days of treatment, or if the discharge changes from clear to thick and colored, contact your vet, as the treatment plan may need adjusting.
Herpesvirus-related conjunctivitis can be more unpredictable. Individual flare-ups typically resolve in the same two-to-three-week window, but some cats experience chronic, low-grade symptoms between episodes. Cats with frequent recurrences may benefit from having antiviral medication on hand so treatment can start at the first sign of a flare-up.
Signs That Something More Serious Is Happening
Simple conjunctivitis causes redness, discharge, and squinting, but the eye itself should look normal in size and shape. If you notice one eye appearing larger than the other, cloudiness developing inside the eye, or a pupil that stays dilated and doesn’t react to light, those point toward conditions like glaucoma or uveitis that require urgent care. These signs tend to develop gradually, so comparing your cat’s eyes to each other is one of the easiest ways to spot a problem early.
A cat that stops eating, develops a fever, or shows nasal discharge alongside eye symptoms may have an upper respiratory infection rather than isolated conjunctivitis. Kittens and elderly or immunocompromised cats are especially vulnerable to these infections becoming serious quickly.