Cat Conjunctivitis and Eye Discharge: Signs and Treatment

Cat conjunctivitis — redness and discharge from one or both eyes — is one of the most common feline health problems, and in most cases it is caused by an infectious agent rather than allergies. Feline herpesvirus-1 (FHV-1) is the single most frequent culprit, responsible for up to 80% of infectious conjunctivitis cases. Treatment depends on the underlying cause, and untreated cases can lead to corneal scarring and permanent vision damage.

Last reviewed: June 2026

Causes and Signs of Cat Eye Discharge

Conjunctivitis means inflammation of the conjunctiva — the pink mucous membrane lining the inner eyelids and the visible white part of the eye. In cats, causes fall into two broad categories:

Infectious:

• Feline herpesvirus-1 (FHV-1): The most common cause. Most cats are infected as kittens; the virus then lies dormant and can reactivate during stress, illness, or steroid use. Signs include watery to mucoid discharge, squinting (blepharospasm), nasal discharge, and sneezing. Corneal ulceration can develop with active FHV-1 replication.
• Chlamydophila felis: Bacterial conjunctivitis that often starts in one eye and spreads to both. Discharge tends to be thick and purulent.
• Mycoplasma felis: Associated with chemosis (pronounced swelling of the conjunctiva) and moderate discharge.
• Calicivirus: Typically accompanied by oral ulcers and upper respiratory signs.

Non-infectious:

• Anatomical causes (entropion, distichiasis — eyelash abnormalities)
• Foreign body
• Dust or environmental irritants

Signs that point to conjunctivitis rather than a deeper eye problem:

• Redness confined to the conjunctiva (not the iris or cornea)
• Watery, mucoid, or purulent discharge from one or both eyes
• Squinting or partial eye closure
• Third eyelid (nictitating membrane) visible or protruding
• Pawing at the eye

According to Fossum's Small Animal Surgery, corneal involvement — indicated by cloudiness, fluorescein stain retention (a corneal ulcer), or abnormal pupil response — changes the urgency of the situation and requires same-day evaluation.

Treatment Options by Cause

Accurate diagnosis guides treatment. A vet will perform a fluorescein stain test, Schirmer tear test, and in some cases conjunctival cytology or PCR to identify the causative agent.

FHV-1: No cure — the virus persists. Antiviral eye drops (idoxuridine or cidofovir) combined with oral famciclovir (90 mg/kg every 8–12 hours in cats) reduce viral replication. L-lysine supplementation has historically been recommended but its evidence base is limited per Drazenovich et al., 2009, JFMS. Stress reduction and immune support are important.

Chlamydophila: Doxycycline (10 mg/kg once daily) for 4 weeks is the treatment of choice. Topical tetracycline ophthalmic ointment is an alternative but systemic treatment is preferred for complete resolution.

Mycoplasma: Responds to topical or systemic doxycycline or azithromycin.

Non-infectious: Remove the inciting cause; lubricating eye drops may provide relief.

Treatment costs for uncomplicated conjunctivitis typically run $100–300 for exam and medications. Cases requiring specialist ophthalmology referral or corneal surgery can cost $500–2,500.

When to See a Vet

Call your vet today if:

• Your cat has persistent eye discharge lasting more than 24–48 hours
• The eye appears cloudy, the pupil looks abnormal, or the eye seems painful (squinting, pawing, light sensitivity)
• Discharge is thick, yellow-green, or blood-tinged
• The third eyelid is clearly elevated and not resolving
• Your cat has a known history of FHV-1 and is showing an acute flare

Go to the ER immediately if:

• The eye appears sunken, severely swollen, or has an obvious wound or foreign object
• Your cat is pawing so aggressively at the eye that you suspect self-trauma
• Eye cloudiness came on suddenly and is complete (could indicate glaucoma or uveitis, not just conjunctivitis)

Frequently Asked Questions

How much does treating cat eye discharge cost? A routine exam with fluorescein stain and Schirmer tear test runs $80–180. Eye drops or ointment plus oral antiviral or antibiotic medication typically adds $50–150. If referral to a veterinary ophthalmologist is needed, consultation fees are $200–400, with procedures costing more.

Is cat conjunctivitis contagious to humans? Feline herpesvirus-1 does not infect humans. Chlamydophila felis can occasionally cause mild conjunctivitis in immunocompromised people, though human infection is rare. Wash your hands after handling an affected cat's face and avoid rubbing your own eyes.

Can I use human eye drops on my cat? No. Never use human eye drops, especially those containing steroids, without veterinary guidance. Steroid-containing drops applied to a herpetic ulcer can cause rapid, catastrophic corneal melting. Only use products specifically prescribed or approved for your cat.

Why does my cat keep getting eye infections? Recurrent episodes are most commonly caused by FHV-1 reactivation. Stress — a new pet, travel, illness, or even seasonal changes — is the most common trigger. The AAFP-AAHA Feline Life Stage Guidelines, 2021 note that minimizing stressors and maintaining consistent routines can reduce flare frequency in FHV-1-positive cats.

Do kittens get eye infections more often? Yes. Kittens are exposed to FHV-1 and Chlamydophila through their mothers and littermates, and their immature immune systems make them more susceptible. Neonatal ophthalmia — purulent eye discharge before the eyelids open — requires urgent veterinary care to prevent permanent eyelid adhesion.

Still Not Sure if Your Cat Needs a Vet?

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