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Cat Eye Discharge: Causes, Treatment and When to See a Vet

A small amount of discharge in the corner of a cat's eye is usually normal, but coloured, excessive or persistent discharge is a sign that something needs attention. Eye conditions in cats can progress quickly, and some can threaten sight without prompt treatment.

Normal vs Abnormal Eye Discharge

Small amounts of clear or slightly darkened discharge (often called 'sleep' or 'eye bogies') in the inner corner of the eye are normal in cats. This represents dried secretions from the eye's natural tear film and doesn't indicate disease.

Abnormal discharge is: copious (much more than a small fleck); coloured — yellow, green or cloudy white, suggesting infection; watery and excessive, suggesting irritation or blocked tear ducts; associated with redness, swelling or apparent eye pain; or causing crusting that sticks the eyelids together.

Bilateral (both eyes) discharge with sneezing and lethargy suggests cat flu (upper respiratory infection). Unilateral (one eye) discharge with pain suggests a localised eye problem — corneal ulcer, foreign body or glaucoma — that needs prompt assessment.

Cat Flu: The Most Common Cause of Eye Discharge

Feline herpesvirus (FHV-1) and feline calicivirus (FCV) — the viruses causing cat flu — are the most common cause of eye discharge in cats, particularly kittens and young adults. Alongside eye discharge, cat flu causes sneezing, nasal discharge, mouth ulcers and lethargy.

Feline herpesvirus is particularly important because once infected, cats remain lifelong carriers. The virus can reactivate during stress, causing recurrent bouts of conjunctivitis and eye discharge, sometimes years after the initial infection. This is why vets sometimes recommend long-term antiviral eye drops (cidofovir) for persistently affected cats.

Treatment of acute cat flu includes supportive care, keeping the eyes and nose clean, encouraging eating (warming food enhances smell), and antibiotic eye drops if secondary bacterial infection is suspected.

Conjunctivitis and Chlamydia

Conjunctivitis — inflammation of the conjunctiva (the membrane lining the eyelids and outer eye) — causes redness, swelling and discharge. It can be caused by viruses (FHV-1), bacteria, chlamydia or irritants.

Feline chlamydia (Chlamydophila felis) is a bacterial infection causing persistent, sometimes severe conjunctivitis, usually starting in one eye before spreading to the other. It's particularly common in multi-cat environments. Treatment involves topical antibiotic eye drops and sometimes systemic doxycycline for 4–6 weeks.

Vaccination against chlamydia is available and is included in some UK feline vaccination products. Your vet can advise whether it's appropriate based on your cat's lifestyle and risk.

Blocked Tear Ducts and Breed Considerations

The nasolacrimal (tear drainage) ducts run from the inner corner of each eye down to the nasal passages. If these become blocked or narrowed — due to chronic infection, scarring or anatomical abnormality — tears overflow onto the face, causing persistent tear staining and discharge.

Brachycephalic cats (Persians, Exotic Shorthairs) are particularly prone to blocked or abnormal tear ducts due to their compressed facial anatomy. Tear overflow causes the characteristic reddish-brown staining seen on the faces of many flat-faced cats. Regular gentle cleaning of the face helps manage this, but doesn't resolve the underlying anatomy.

Nasolacrimal duct flushing or surgery can help in some cases. Discuss options with a veterinary ophthalmologist if tear staining is severe and affecting the cat's comfort or skin condition.

Corneal Ulcers and Eye Emergencies

A corneal ulcer (a scratch or erosion on the surface of the eye) causes pain, squinting, excessive tear production and sometimes a cloudy area on the eye. This is an urgent condition — untreated corneal ulcers can deepen and perforate the eye, causing permanent damage or loss of the eye.

Signs of eye pain that warrant same-day vet attention include: squinting or keeping the eye closed; obvious cloudiness or opacity to the cornea; excessive tearing from one eye; pawing at the face or eye; blue or red discolouration of the eye.

Glaucoma in cats — elevated intraocular pressure — causes acute cloudiness and pain and can cause rapid, permanent vision loss. Any sudden change in eye appearance combined with apparent pain is an ophthalmic emergency.

Find a Vet Near You

Eye conditions in cats can progress quickly. If your cat has coloured discharge, apparent eye pain or sudden changes to eye appearance, book a vet appointment promptly. Use CompareMyVet at app.comparemyvet.uk to find and compare practices near you.