You notice your cat squinting slightly, and when you look closer, one eye has discharge in the corner. The discharge might be clear and watery, thick and goopy, or crusty and dried on the fur around the eye. The other eye looks completely normal. Your cat doesn’t seem particularly bothered, but the discharge keeps returning even after you gently wipe it away.

Eye discharge affecting only one eye typically signals a problem localized to that specific eye rather than a systemic illness. When both eyes have discharge, viral infections or general health problems are more likely. When just one eye is affected, you’re usually dealing with something that happened directly to that eye, such as an injury, foreign object, or localized infection.

Conjunctivitis, which is inflammation of the conjunctiva (the pink tissue lining the eyelids and covering the white part of the eye), is the most common cause of eye discharge in cats. However, “conjunctivitis” is a symptom description rather than a diagnosis. Understanding what’s causing the conjunctivitis in that specific eye determines the appropriate treatment.

This guide explains the common causes of one-eye discharge in cats, how to distinguish between different types of conjunctivitis, what treatments work for each cause, and when eye discharge represents an emergency requiring immediate veterinary care.

Understanding the Types of Eye Discharge

The appearance of the discharge provides important diagnostic clues about what’s causing the problem.

Clear, Watery Discharge

Clear, thin discharge that looks like tears suggests:

Mild irritation
Blocked tear duct
Early viral infection
Allergies
Foreign material causing tearing

This type of discharge isn’t infected yet, though it can progress to thicker discharge if the underlying cause isn’t addressed.

Thick, Mucoid Discharge

Thick, stringy, mucus-like discharge (white, gray, or yellowish) indicates:

More significant inflammation
Possible bacterial component
Dry eye (inadequate tear production)
Chronic irritation

This discharge suggests the conjunctiva is producing mucus in response to irritation or trying to compensate for inadequate tear production.

Yellow or Green Discharge

Thick, colored discharge clearly indicates bacterial infection. The yellow or green color comes from white blood cells fighting infection. This type of discharge:

Is pus-like in consistency
Crusts heavily on the fur and eyelids
Often glues the eye partially shut, especially after sleep
Has a distinct appearance different from normal tears

Bloody Discharge

Blood-tinged discharge is less common but suggests:

Trauma to the eye
Severe infection
Ulceration of the cornea
Foreign object causing damage
Sometimes tumors or serious conditions

Any bloody discharge warrants prompt veterinary evaluation.

Crusty, Dried Discharge

Crusty material on the fur around the eye or at the corners is dried discharge. The original discharge could have been any type, but it accumulated and dried while your cat slept or when discharge production exceeded her ability to clean it away.

Crusty discharge indicates:

The problem has been ongoing for at least several hours
Discharge is being produced faster than normal
Your cat might be uncomfortable and not grooming normally

Causes of One-Eye Discharge

When only one eye is affected, certain causes are more likely than others.

Corneal Injury or Ulcer

The cornea is the clear outer surface of the eye. Scratches, ulcers, or other damage to the cornea create pain and trigger excessive tearing or discharge from that eye only.

How corneal injuries happen:

Scratches from cat fights or rough play
Pokes from plant material or grass
Self-inflicted trauma from rubbing an already irritated eye
Chemical irritation (cleaners, soaps, medications)
Foreign objects scratching the surface

Symptoms of corneal problems:

Squinting or keeping the eye partially closed (blepharospasm)
Excessive tearing initially, possibly progressing to thicker discharge if infection develops
Sensitivity to light (photophobia)
Pawing at the affected eye
The eye might look cloudy or have a dull spot on the cornea
Often significant discomfort

Corneal ulcers are serious because they can worsen rapidly and potentially cause permanent vision damage. The eye itself is in pain, triggering protective discharge and squinting.

Foreign Object

Something lodged in or around the eye creates irritation and discharge as the eye tries to flush out the irritant.

Common foreign objects:

Plant seeds or awns (especially foxtails in certain regions)
Dust or debris
Hair or fur
Small particles of sand or dirt
Eyelashes growing abnormally and rubbing the eye

Foreign object symptoms:

Sudden onset of discharge and discomfort
Constant pawing at the eye
Rubbing the face on surfaces
Excessive blinking or squinting
Discharge from just one eye
Sometimes you can see the foreign material, but often it’s hidden under the third eyelid or tucked in the conjunctival folds

Foreign objects require removal for symptoms to resolve. The eye will continue producing discharge until the irritant is gone.

Bacterial Conjunctivitis

Bacterial infections of the conjunctiva cause inflammation and pus-like discharge. In cats, bacterial conjunctivitis affecting just one eye often results from:

Secondary infection following injury or irritation
Contamination from a dirty paw used to rub the eye
Spread from an upper respiratory infection that predominantly affects one eye

Primary bacterial conjunctivitis (without an underlying cause) is less common in cats than in dogs or humans.

Bacterial conjunctivitis symptoms:

Yellow or green thick discharge
Redness and swelling of the conjunctiva
Eyelids may stick together
Crusty accumulation on the eyelids and fur
Usually one eye, though both can be affected
The cat might squint but often shows less discomfort than with corneal injuries

Viral Conjunctivitis (Feline Herpesvirus)

Feline herpesvirus is the most common viral cause of eye problems in cats. While herpesvirus often affects both eyes, it can affect one eye more severely than the other or occasionally just one eye.

Herpesvirus eye symptoms:

Can start as clear discharge, progressing to thicker discharge
Often accompanied by sneezing or nasal discharge
May cause corneal ulcers
Tends to recur throughout the cat’s life during stress
Young cats and cats from shelters commonly affected

Most cats exposed to herpesvirus carry it for life. The virus lies dormant and reactivates during stress, illness, or immune suppression.

Blocked Tear Duct

Tear ducts drain tears from the eye into the nasal cavity. When a duct blocks, tears overflow onto the face instead of draining normally.

Blocked tear duct symptoms:

Constant clear or slightly discolored discharge
Wetness and staining on the fur below the eye
Usually one eye affected (though both ducts can block)
No pain or squinting
The eye itself looks relatively normal except for overflow tearing
More common in flat-faced breeds (Persians, Himalayans)

Blocked ducts might resolve spontaneously or require veterinary flushing to open them.

Entropion

Entropion means the eyelid rolls inward, causing the eyelashes and lid edge to rub against the cornea constantly. This creates chronic irritation and discharge.

Entropion symptoms:

Persistent discharge from the affected eye
Squinting or discomfort
The eyelid margin appears to roll inward
Can affect upper or lower lids
More common in certain breeds (Persians, Himalayans)
Usually present from young age but sometimes develops later

Entropion requires surgical correction. Medical management alone doesn’t solve the mechanical problem.

Allergies

While allergies more commonly affect both eyes, sometimes one eye is more affected than the other, especially if localized exposure occurred (your cat rubbed one side of her face against an allergen).

Allergic conjunctivitis symptoms:

Clear to slightly milky discharge
Itching (rubbing and pawing at eyes)
Redness without thick discharge
Often accompanies skin allergies
May be seasonal
Both eyes usually involved to some degree

Tumors or Masses

Rarely, tumors or benign masses in or around the eye cause discharge due to irritation or blocked drainage.

Tumor-related symptoms:

Progressive worsening over weeks to months
Visible mass or swelling
Usually one eye affected
Often affects older cats
Discharge that doesn’t respond to typical treatments

Dry Eye (Keratoconjunctivitis Sicca)

Dry eye means inadequate tear production. Without enough tears, the eye becomes irritated and produces thick, mucoid discharge as a poor substitute for natural lubrication.

Dry eye symptoms:

Thick, sticky, stringy discharge
Dull, dry appearance to the cornea
Redness and irritation
Can affect one or both eyes
Eye appears uncomfortable
Sometimes has a characteristic “dry” look

Dry eye in cats is less common than in dogs but does occur, especially following certain infections or immune-mediated conditions.

When One Eye Discharge is More Serious

Certain accompanying signs indicate more serious problems requiring urgent care.

Red flags requiring same-day veterinary attention:

Cloudy or hazy appearance to the eye itself
Visible defect or divot on the cornea
Eye appears swollen or bulging
Extreme pain (cat won’t let you near the eye)
Pupils are different sizes
The eye looks collapsed or sunken
Bloody discharge
Vision seems impaired in the affected eye
Cat is systemically ill (not eating, lethargic)

Urgent but not emergency:

Thick yellow or green discharge
Significant squinting
Persistent clear discharge for more than 2 to 3 days
Discharge getting progressively worse
Cat constantly pawing at the eye

Can monitor briefly at home:

Small amount of clear discharge
No squinting or apparent discomfort
Started just today
Cat is otherwise completely normal

Even conditions you can monitor briefly should prompt a veterinary visit if they don’t resolve within 24 to 48 hours or if they worsen at all.

What You Can Do at Home

When you first notice one-eye discharge, you can take some initial steps while determining whether veterinary care is needed.

Clean the Eye Gently

Keeping the eye clean helps your cat feel more comfortable and allows you to better assess the problem.

How to clean eye discharge:

Use warm water on a soft cloth or cotton ball
Wipe gently from the inner corner of the eye outward
Use a fresh section of cloth for each wipe
Don’t wipe back and forth, which spreads bacteria
Clean away dried crusty material carefully
Don’t touch the eyeball itself

Clean the eye several times daily while discharge is present. This removes irritating material and prevents heavy crusting.

Look for Obvious Foreign Objects

In good light, examine the eye carefully:

Gently lift the upper and lower eyelids
Look in the corners of the eye
Check if you can see any debris or foreign material
Observe whether the third eyelid (inner eyelid) is covering more of the eye than normal

Don’t probe or try to remove embedded foreign objects yourself. Superficial debris at the very corner might be wiped away, but anything touching the eye surface or cornea needs professional removal.

Avoid Home Remedies Without Veterinary Guidance

Don’t apply anything to the eye without specific veterinary instruction:

No human eye drops
No tea bags, honey, or other folk remedies
No leftover eye medication from previous cats or other pets
No hydrogen peroxide or alcohol-based products

The eye is delicate and sensitive. Inappropriate products can cause serious damage.

Prevent Self-Trauma

If your cat is pawing or rubbing at the eye excessively, she might be making the problem worse.

Options to prevent self-injury:

Elizabethan collar (cone) prevents pawing at the face
Soft fabric collars work for some cats
Trim nail tips to reduce damage if scratching does occur
Distract with play or treats when you see pawing behavior starting

Monitor Carefully

Track the discharge over 24 to 48 hours:

Is it getting better, worse, or staying the same?
Is the amount increasing?
Is the color changing (clear to yellow suggests developing infection)?
Is squinting getting worse?
Are new symptoms developing?

This information helps your veterinarian assess urgency and progression.

Veterinary Diagnosis

Your veterinarian uses several methods to diagnose the cause of eye discharge.

Ophthalmic Examination

A thorough eye exam includes:

Visual inspection checks for obvious abnormalities, discharge characteristics, redness, swelling, masses, or asymmetry between eyes.

Ophthalmoscope examination allows detailed viewing of the cornea, lens, and internal eye structures.

Checking pupil response tests neurological function and rules out certain serious conditions.

Third eyelid examination involves flipping up the third eyelid to check for foreign objects hidden behind it.

Fluorescein Stain Test

This is the gold standard test for corneal ulcers:

A drop of fluorescent dye is placed in the eye
The dye is washed away with saline
The eye is examined under special light
Areas where the corneal surface is damaged hold the dye and glow bright green
Healthy cornea doesn’t retain the dye

This test is painless and immediately shows whether corneal injury is present.

Schirmer Tear Test

This test measures tear production to check for dry eye:

A small paper strip is placed in the lower eyelid
Left in place for 60 seconds
The length of moistened paper is measured
Normal cats wet at least 10-15mm of the strip per minute
Less than this indicates inadequate tear production

Intraocular Pressure

If glaucoma is suspected, pressure inside the eye is measured with a special instrument. This is usually done by specialists or practices with specific equipment.

Cytology

A sample of discharge can be examined microscopically to check for:

Types of inflammatory cells present
Bacteria
Unusual cells suggesting tumors

Culture

For severe or non-responsive infections, discharge can be cultured to identify specific bacteria and determine which antibiotics work best against them.

Treatment Options

Treatment depends entirely on what’s causing the discharge.

For Bacterial Conjunctivitis

Antibiotic eye drops or ointment is the primary treatment. Common options include:

Triple antibiotic ophthalmic ointment
Terramycin (oxytetracycline)
Tobramycin drops
Gentamicin ointment

Application frequency:

Usually 3 to 4 times daily
Treatment typically lasts 7 to 14 days
Continue for several days after symptoms resolve to prevent recurrence

How to apply eye medication:

Gently restrain your cat
Pull down the lower eyelid slightly
Apply ointment to the inside of the lower lid, or drop liquid medication directly on the eye
Allow your cat to blink, distributing the medication
Reward with treats to create positive associations

Warm compresses can supplement medication:

Soak a clean cloth in warm water
Hold gently against the closed eye for a few minutes
This loosens dried discharge and soothes irritation
Do this 2 to 3 times daily

For Viral Conjunctivitis (Herpesvirus)

Antiviral medications target the virus:

Famciclovir (oral antiviral) is most effective
Idoxuridine eye drops (less commonly used)
Cidofovir (topical, used in some cases)

L-lysine supplementation might help:

Amino acid that may suppress herpesvirus replication
Available as powder, treats, or paste
Evidence is mixed but commonly recommended
Safe with minimal side effects

Supportive care:

Keeping eyes clean
Using artificial tears to flush debris
Ensuring adequate hydration and nutrition
Reducing stress

Management of ulcers: If herpesvirus has caused corneal ulcers, additional treatment addresses the ulceration specifically.

Herpesvirus cannot be cured, only managed during flare-ups. The virus remains dormant between episodes.

For Corneal Ulcers

Antibiotic drops or ointment prevents secondary bacterial infection of the ulcer.

Atropine drops in some cases:

Dilates the pupil
Reduces pain from muscle spasms in the eye
Used for deeper or more painful ulcers

Elizabethan collar is essential:

Prevents rubbing and pawing
Allows the ulcer to heal undisturbed
Usually needed for the entire treatment period

Pain medication for significant discomfort.

Rechecks with fluorescein staining monitor healing:

Simple ulcers heal in 5 to 7 days
Deeper ulcers take longer
Non-healing ulcers need specialist referral

Surgery for complicated ulcers:

Deep ulcers at risk of rupture
Indolent ulcers (not healing with medical treatment)
Requires specialist veterinary ophthalmologist

For Foreign Objects

Removal under magnification with proper tools:

Often requires sedation or anesthesia for safe removal
Your vet irrigates the eye thoroughly
Sometimes foreign objects are embedded and need careful extraction

Post-removal treatment:

Antibiotic eye medication to prevent infection
Treatment for any corneal damage the object caused
Usually heals quickly once the irritant is removed

For Blocked Tear Ducts

Flushing the tear duct clears the obstruction:

Usually requires sedation
A catheter is threaded through the duct
Saline is flushed through under pressure
Clears most blockages effectively

Ongoing management if blockage recurs:

Keeping the eye clean
Sometimes daily wiping is needed long-term
Repeat flushing if necessary

For Entropion

Surgical correction is the definitive treatment:

The eyelid is repositioned surgically
Usually requires referral to a specialist
Very successful with excellent outcomes

Temporary management before surgery:

Lubricating eye ointments
Antibiotics if secondary infection develops
Keeping discharge cleaned away

For Dry Eye

Artificial tears supplement natural tear production:

Applied 4 to 6 times daily or more
Keeps the cornea moist and comfortable
Various products available

Cyclosporine or tacrolimus ointment stimulates tear production:

Takes 4 to 6 weeks to see full effect
Requires long-term use
Very effective in many cats

Treating underlying causes if identified.

For Allergies

Antihistamine eye drops reduce allergic inflammation.

Corticosteroid eye drops for more severe cases:

Very effective at reducing inflammation
Used carefully, as they can worsen certain conditions
Never used if corneal ulcers are present

Systemic allergy management:

Addressing environmental allergens
Diet trials for food allergies
Oral antihistamines or steroids in some cases

Preventing Eye Problems

While not all eye problems can be prevented, certain strategies reduce risk.

For cats prone to herpesvirus flare-ups:

Minimize stress
L-lysine supplementation
Keep up with vaccinations
Treat flare-ups promptly before they become severe

General eye health:

Keep your cat’s face clean
Trim hair around the eyes in long-haired breeds
Prevent cat fights
Keep hazardous chemicals away from cats
Monitor eyes during grooming for early detection of problems

For flat-faced breeds:

Extra attention to eye cleaning
Watch for signs of entropion or chronic irritation
Regular veterinary eye checks

Indoor cats:

Significantly reduced risk of injuries and foreign objects
Less exposure to infectious diseases
Lower risk of trauma from fights

When Treatment Isn’t Working

Sometimes initial treatment doesn’t resolve the problem.

Contact your veterinarian if:

No improvement after 3 to 4 days of treatment
Symptoms get worse despite medication
New symptoms develop
Your cat won’t allow medication application
The problem resolves but quickly recurs

Lack of response might mean:

Wrong diagnosis (treating bacterial infection when the real cause is viral or mechanical)
Resistant bacteria requiring different antibiotics
Underlying cause not addressed (foreign object still present, ulcer not healing)
Serious condition like tumor or immune-mediated disease

Your vet might recommend:

Culture and sensitivity testing
Referral to a veterinary ophthalmologist
Different medications
Additional diagnostic tests

Frequently Asked Questions

Can I use human eye drops on my cat?

No, don’t use human eye drops without veterinary guidance. Many human products contain ingredients that are harmful to cats or inappropriate for certain eye conditions. For example, drops containing steroids can cause serious problems if a corneal ulcer is present. Artificial tears specifically labeled for use in cats or as veterinarian-approved are the only safe over-the-counter option, and even these should be temporary until you get proper diagnosis.

Why is only one eye affected if it’s an infection?

One-eye involvement usually means the problem originated in that specific eye rather than from systemic illness. Injuries, foreign objects, or localized bacterial infections naturally affect just the injured or contaminated eye. Even with viral infections like herpesvirus, one eye can be more severely affected if that eye sustained injury or had more viral particles introduced during grooming or face rubbing.

How long does conjunctivitis take to heal?

Simple bacterial conjunctivitis usually improves within 3 to 5 days of starting antibiotics, with complete resolution in 7 to 14 days. Viral conjunctivitis takes longer, often 2 to 3 weeks. Conjunctivitis from corneal ulcers resolves as the ulcer heals, typically 7 to 14 days for simple ulcers. Chronic conditions like dry eye or allergies require ongoing management rather than cure.

My cat’s eye discharge is clear. Do I still need to see a vet?

Clear discharge for a day or two might resolve on its own, especially if caused by mild irritation. However, if clear discharge persists beyond 2 to 3 days, progressively worsens, or is accompanied by squinting, redness, or your cat pawing at the eye, veterinary examination is warranted. Clear discharge can be an early stage that progresses to infection, or it might indicate conditions like blocked tear ducts or allergies that need treatment.

Can eye infections spread to other cats in my household?

Bacterial conjunctivitis is minimally contagious between cats, as it usually results from individual factors rather than highly infectious bacteria. However, viral conjunctivitis from herpesvirus is contagious through direct contact or contaminated surfaces. If one cat has herpesvirus, others in the household are likely also exposed or carriers. Practice good hygiene, wash hands between handling cats, and separate food bowls and litter boxes if possible during active infections.

Is it safe to wait and see if eye discharge goes away on its own?

Minor clear discharge with no other symptoms can be monitored for 24 to 48 hours. However, eye problems can deteriorate quickly. Corneal ulcers can perforate (rupture), infections can worsen, and foreign objects can work deeper into tissues. If discharge hasn’t improved within 2 days, is getting worse, involves squinting or apparent pain, or is thick and colored, don’t continue waiting. Early treatment prevents serious complications and permanent vision damage.

Why does the discharge keep coming back even after treatment?

Recurring discharge suggests either incomplete treatment of the original problem, an underlying cause that wasn’t addressed, or a chronic condition. Possibilities include: herpesvirus that’s flaring up repeatedly, allergies that need long-term management, anatomical problems like entropion, dry eye requiring ongoing treatment, or blocked tear ducts. Your vet needs to investigate underlying causes rather than just treating symptoms each time they appear.

My cat won’t let me put drops in her eye. What alternatives exist?

Some options for difficult-to-medicate cats include: oral medications instead of eye drops (like oral antibiotics or famciclovir for herpesvirus), less frequent application schedules (some medications work with once or twice daily dosing), ointments that are easier to apply than drops for some people, or having your veterinarian give long-acting injections when appropriate. Ask your vet about alternatives, but don’t skip treatment altogether, as eye problems can become serious without proper care.

Cat Eye Discharge One Eye: Conjunctivitis Treatment