Cat Health
Cat Eye Discharge: UK Causes, Care & When to See a Vet
Published Last updated 4 min read
Quick answer
Small amounts of clear discharge may be normal in flat-faced breeds or after sleep. Thick yellow or green discharge, squinting, redness, or cloudiness needs a vet — often cat flu, infection, or a corneal ulcer. Eye problems in cats can progress quickly and should not wait.
Normal discharge vs illness
A trace of clear moisture or light crusting after sleep is common. Persians and other flat-faced breeds often have tear staining from blocked tear ducts — this is cosmetic unless the eye looks sore.
Usually harmless:
- Clear discharge without squinting or redness
- Light sleep crusting that wipes away easily
- Tear staining in Persians without pain signs
Needs investigation:
- Yellow, green, or bloody discharge
- Squinting or keeping the eye closed
- Red or swollen eyelids
- Cloudy or scratched cornea
- Discharge with sneezing or fast breathing
Common causes in UK cats
| Cause | Typical signs | Notes |
|---|---|---|
| Cat flu (URI) | Watery then thick discharge, sneezing | Herpesvirus and calicivirus — see Respiratory infection |
| Bacterial conjunctivitis | Yellow-green pus, red eye | Often secondary to viral infection |
| Blocked tear ducts | Constant wetness, tear staining | Common in Persians |
| Corneal ulcer | Squinting, watery or cloudy eye | Painful — same-day vet care |
| Allergies and irritants | Clear discharge, rubbing face | Smoke, dust, perfumed litter |
| Foreign body | Sudden squinting | Dust, hair, or grass under eyelid |
| Glaucoma | Red, painful, enlarged eye | Emergency — vision at risk |
Infectious causes
Cat flu is a common cause of conjunctivitis in the UK, especially in kittens and unvaccinated cats. Discharge may start watery and become thick. Sneezing, mouth ulcers, and fever can accompany eye signs. Vaccination reduces severity but does not eliminate all viruses.
When to see a vet urgently
Phone your vet the same day or use emergency out-of-hours care if:
- Your cat is squinting or will not open the eye
- The eye looks cloudy, blue, or scratched
- Thick green or yellow discharge with lethargy
- Bulging or very swollen eye
- Discharge with open-mouth breathing — see Cat breathing fast
- Kitten with sealed-shut eyes or heavy discharge
Book a routine appointment within a few days for mild discharge that persists more than 48 hours without squinting.
Home care before your appointment
While waiting for a vet visit, note:
- Which eye is affected — photograph discharge if safe
- Vaccination status and contact with other cats
- Other symptoms — sneezing, not eating, or drooling
- When symptoms started and whether they are worsening
What you can do at home:
- Gently wipe discharge with cooled boiled water — one cloth per eye
- Wipe from the inner corner outward
- Prevent pawing at the eye — a cone if advised
- Isolate from other cats if cat flu is suspected
What not to do:
- Do not use human eye drops without vet advice
- Do not share cloths between cats if infection is suspected
- Do not delay if your cat is squinting
What your vet may do
Examination may include corneal staining, checking tear production, and assessing for ulcers. Your vet might recommend:
- Antibiotic or antiviral drops for infection or cat flu
- L-lysine or supportive care for recurrent herpesvirus flare-ups
- Foreign body removal if needed
- Referral for glaucoma, deep ulcers, or surgery
Treatment depends on cause — ulcers need prompt care; chronic cat flu may need long-term management. See Cat dental care UK if oral health contributes to overall wellbeing.
Related guides
Sources & further reading
Facts in this guide are rewritten in plain English from publicly available UK advice. We name the organisation where a specific point comes from their guidance. Links below go to the original pages — use them to read the source material directly.
PETHEALTH+ is independent. These organisations do not sponsor, approve, or partner with this website. Guidance checked against sources listed below (last updated 2026-06-25).
Related guides
- Cat Sneezing: Common Causes, Home Care & When to Worry
- Cat Breathing Fast: UK Emergency Signs & Common Causes
- Cat Respiratory Infections UK — URI Symptoms, Causes & Treatment
- Cat Not Eating: Causes, How Long Is Safe & When to See a Vet
- Why Is My Cat Drooling Excessively? UK Causes & When to Worry
- Cat Dental Care UK — Brushing, Gum Disease & Vet Treatment
Frequently Asked Questions
- Is cat eye discharge contagious?
- Viral cat flu can spread between cats in the same household. Isolate new cases if possible and wash hands after handling. Discharge from blocked tear ducts alone is not contagious.
- Can allergies cause runny eyes in cats?
- Yes — dust, pollen, and smoke can irritate eyes. Allergies usually cause clear discharge without squinting, but persistent signs still deserve a vet check.
- When is eye discharge urgent in cats?
- Squinting, a bulging eye, thick green pus, or a cloudy cornea needs same-day care. Corneal ulcers are painful and can worsen within hours.
- Do kittens get eye infections?
- Yes — neonatal conjunctivitis is common without early vet care, especially in kittens from feral or multi-cat backgrounds. Prompt treatment protects vision.