Conjunctivitis in Cats: More Common Than You Might Think
Conjunctivitis is one of the most frequently diagnosed eye conditions in cats, yet it is also one that many owners initially dismiss as a passing irritation. The conjunctiva refers to the moist, pink tissue lining the inside of the eyelids and the visible white portion of the eye. When this tissue becomes inflamed, the condition is called conjunctivitis — colloquially known as pink eye.
In cats, conjunctivitis can be infectious or non-infectious, and identifying the underlying cause matters enormously when it comes to choosing the right treatment and preventing it from returning.
What Causes Conjunctivitis in Cats?
Unlike in humans, where viral conjunctivitis is often a straightforward and self-limiting illness, feline conjunctivitis is frequently tied to more complex causes.
Feline Herpesvirus (FHV-1)
This is by far the most common infectious cause of conjunctivitis in cats. Feline herpesvirus is estimated to infect the vast majority of domestic cats at some point in their lives, often contracted as kittens from their mothers or in multi-cat environments. The virus causes acute episodes of eye inflammation, typically accompanied by nasal discharge, sneezing and lethargy.
Like its human equivalent, feline herpesvirus never fully leaves the body. It remains dormant within nerve tissue and can reactivate during periods of stress — a house move, a new pet, illness, or even a change in routine. This latency is why some cats suffer from recurrent bouts throughout their lives.
Chlamydophila Felis
This bacterial organism is a significant cause of conjunctivitis in cats, particularly in multi-cat households and catteries. Infection typically begins in one eye before spreading to the other, and the discharge tends to be more purulent than that seen with herpesvirus alone. Chlamydophila responds well to appropriate antibiotic treatment, making accurate diagnosis important.
Mycoplasma
Mycoplasma species are another bacterial cause of feline conjunctivitis, often found alongside other pathogens rather than as a sole infection. They are associated with similar symptoms to chlamydophila and respond to similar antibiotic classes.
Non-Infectious Causes
Not all conjunctivitis is driven by infection. Environmental irritants including dust, smoke, cleaning product fumes and pollen can trigger inflammation. Allergic conjunctivitis, while less common in cats than dogs, does occur. Foreign bodies and physical injury to the conjunctival tissue are also potential triggers.
Recognising the Symptoms
The hallmark signs of conjunctivitis in cats include:
- Redness or swelling of the tissue around and inside the eye
- Discharge ranging from clear and watery to thick, yellow or green
- Squinting or keeping one or both eyes partially closed
- Pawing at the face or rubbing against surfaces
- Crusting around the eye, particularly after sleep
- Sensitivity to light
In cases linked to upper respiratory infection, sneezing, nasal discharge and a reduced appetite may accompany the eye symptoms.
Diagnosis and Treatment
Your vet will examine the eye carefully, assess the conjunctival tissue and may take a swab for laboratory analysis to identify the causative organism. This step is particularly valuable in recurrent cases or where initial treatment has not produced the expected response.
Antiviral Treatment for Herpesvirus
There is no cure for feline herpesvirus, but antiviral medications can reduce the severity and duration of flare-ups. Topical antiviral drops or ointments containing cidofovir or idoxuridine are used in some cases, though availability varies. Oral famciclovir has become the preferred systemic option in many practices, showing good results for reducing viral replication during active episodes.
L-lysine supplementation was historically recommended to suppress herpesvirus replication, but more recent research has cast doubt on its effectiveness. Current veterinary consensus is mixed, and you should discuss this with your vet rather than supplementing independently.
Antibiotics for Bacterial Infections
Bacterial causes such as chlamydophila respond well to tetracycline-class antibiotics, typically administered as eye drops or ointment. In more severe cases or where topical treatment is difficult, oral doxycycline may be prescribed. Completing the full course of antibiotics is essential, even if symptoms resolve before the medication is finished.
Supportive Care
Regardless of cause, keeping the eye clean is an important part of home management. Gently removing discharge with a clean, damp cotton pad prevents crusting and reduces the risk of secondary infection. Applying gentle warmth to a crusted-shut eye can help soften the discharge before attempting to clean it.
Preventing Recurrence
Preventing conjunctivitis from returning depends heavily on the underlying cause, but several general measures are beneficial across the board.
For herpesvirus-positive cats, stress management is arguably the most powerful preventive tool available. Providing stable routines, adequate hiding spaces, vertical territory through cat trees and shelves, and minimising household disruption reduces the frequency and severity of reactivation episodes. Pheromone diffusers such as Feliway have reasonable evidence supporting their use in multi-cat households.
Vaccination does not prevent herpesvirus infection but significantly reduces the severity of illness. Ensuring your cat is up to date with their core vaccinations — which include protection against feline herpesvirus and calicivirus — is a straightforward and important step.
In multi-cat environments where bacterial causes are identified, treating all cats simultaneously and maintaining good hygiene between animals is essential. Shared food bowls, bedding and grooming tools can serve as vectors for transmission.
For cats with environmental or allergic triggers, identifying and removing the offending substance is the most effective long-term solution. Air purifiers, fragrance-free cleaning products and regular vacuuming of soft furnishings can make a meaningful difference.
Recurrent conjunctivitis that does not respond adequately to treatment warrants referral to a veterinary ophthalmologist, who can conduct more specialised investigations and offer targeted therapies. With the right approach, most cats with conjunctivitis achieve good long-term control, even when complete cure is not possible.