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Conjunctivitis in Cats—By Dr. Leslie Brooks

Conjunctivitis in Cats—By Dr. Leslie Brooks
Written by Dr. Leslie Brooks, DVM
—Veterinarian 🇺🇸

Conjunctivitis is one of the most common health conditions affecting our domestic cats. If you’ve ever seen your cat’s eyes get red and puffy, your cat was likely dealing with conjunctivitis.

In this article, we will discuss what conjunctivitis is, what the signs are, what causes it, and how to treat it.

What is Conjunctivitis?

Conjunctivitis is an inflammation of the conjunctival tissues of the eye. These are the areas just underneath the eyelids, surrounding the eyes.

Fun fact: cats have what we call a “third eyelid”. It lives hidden under the corner of the eye closest to their nose. There is also conjunctival tissue within this third eyelid.

The conjunctival tissues typically serve to protect and lubricate the eye. When they are inflamed and irritated, though, they can cause your cat’s eyes to be pretty painful.

Signs of Conjunctivitis

Conjunctivitis can sometimes develop overnight. Your cat may look completely normal before you go to bed and when you wake up the next morning you notice your cat’s eyes look very strange.

Other times, conjunctivitis can have a gradual onset. You may notice some extra tearing from one of your cat’s eyes one day. Then, a few days later you may notice their eye looks a little puffy and red.

The onset of signs and symptoms can vary cat to cat and cause to cause. Additionally, conjunctivitis may affect one eye in some cats, and both eyes in other cats.

Here are some tale-tell signs your cat is suffering from conjunctivitis:

  • Excessive tearing
  • Squinting
  • Thick, green, mucoid discharge coming from the eyes
  • Eyes appear reddened, especially underneath the eyelids (normal conjunctiva is a white to very light pink color)
  • Eyes appear swollen, especially underneath and around the eyelids
  • Eyes matted shut
  • Inability to see the full surface of your cat’s eye
  • Excessive rubbing or scratching of the eyes

Depending on the severity and underlying cause of conjunctivitis, these signs may be more or less pronounced in your cat.

Causes of Conjunctivitis

There are many different causes of conjunctivitis in cats. As mentioned before, conjunctivitis is an inflammation of the conjunctival tissues of the eye. So, anything that causes an irritation or disturbance in the conjunctiva can cause conjunctivitis.

That being said, here are some of the typical causes of conjunctivitis in cats:

  • Bacterial Infections
  • Viral Infections
  • Allergies
  • Irritants
  • Inverted Eyelashes
  • Trauma
  • Foreign Objects
  • Cancer

Now, we will break each of these down and discuss them in more detail below.

Bacterial Infections

There are certain bacterial infections that can cause conjunctivitis in cats. One of the most common ones is called Chlamydophila felis (Chlamydia). Chlamydia tends to affect kittens more intensely, but adult cats are definitely susceptible to it as well. It is contagious and is spread by contact with other infected cats.

Viral Infections

Feline Herpes Virus is a common viral cause of conjunctivitis in cats. While it usually doesn’t cause as severe signs as Chlamydia, it does cause tearing, redness, and squinting of the eye. In severe cases, it can also lead to corneal ulcers and vision loss. This is also contagious in nature.

There is no cure or perfect treatment for Feline Herpes Virus. Once a cat has it, it typically stays with them for life. Most cats’ immune system will keep the virus at bay. They will continue to have flare ups of it throughout their life, especially during times of stress or sickness due to other causes.


Seasonal allergies can definitely cause your cat’s conjunctiva to become inflamed. Cats can have allergies at any time of the year. The most common seasons for allergies, though, are spring and fall, with pollen and leaves flying around. If your cat’s eye issues tend to occur during certain times of the year, their eyes get fairly itchy, or they also have some sneezing and/or itchy skin associated with it, they probably have underlying allergies.


Certain substances in the air or home environment can cause irritation to your cat’s eyes, leading to conjunctivitis. The most common causes of this are burning candles, incense, air fresheners, and cigarette smoke.

Inverted Eyelashes or Eyelids

Though rare in cats, some cats can either be born with eyelashes growing in the wrong place, or they can develop them later in life. For the most part, eyelashes are supposed to grow at the outer edge of the eyelids.

It is when they grow on the inner aspect of the eyelid, or they grow in the wrong direction that they cause problems for your cat by constantly rubbing and scratching on the tissues surrounding the eye.

Additionally, if a cat is born and develops with an eyelid that turns in on itself (referred to as “entropion), this too can cause irritation to the conjunctival tissues.


Incidents of trauma can certainly cause conjunctivitis as well. If your cat cuts their eyelid on something, this can harm the conjunctiva and cause irritation. It could also lead to a secondary bacterial infection.

This is a good reason to try to keep your cat’s nails trimmed regularly. If they inadvertently scratch their eye with a nail while tending to an itch on their face or in their ears, this could be problematic for their eye and cause a corneal ulcer.

Foreign Objects

Cats love to play and get into things. It is not surprising that some cats may get something stuck in their eye or eyelid from time to time. This can run the gambit from truly anything. Especially if they like to roam around outside, they may get pieces of grass, leaves, sand, dust, or pollen caught in their conjunctiva.


Cancers affecting the external part of cats’ eyes are very rare but possible. There are certain cancers that may grow as a visible tumor and you may notice it on the conjunctiva of your cat’s eye. There are also cancers, such as Lymphoma, that could infiltrate the conjunctiva of your cat, but not be a visible growth.

Treatment of Conjunctivitis

For some cats, conjunctivitis can be self-limiting. This means, they will improve on their own and it will resolve without any treatment within a couple of days. However, for other cats, and depending on the cause, conjunctivitis can become severe if left untreated.

If you notice signs of conjunctivitis in your cat, you should schedule an appointment with your veterinarian. If conjunctivitis is left untreated and it does not go away on its own within 1-2 days, it can cause long-term consequences for the health of your cat’s eyes and even lead to loss of vision.

Determine the Underlying Cause

Treatment of conjunctivitis first consists of determining the underlying cause. Your veterinarian will use a special light to look at your cat’s eye, underneath their eyelids, and into the back of their eyeball. This will help them determine what the most likely cause is.

Removal of Foreign Material

Based off of their exam, they will recommend a treatment course. If they notice something stuck in your cat’s conjunctiva or an eyelash that is in the wrong place, the treatment would entail sedating your cat to safely remove the object or surgically remove the inappropriate eyelash.

Eye Drops and Ointments

If nothing obvious is found in your cat’s eye, your vet may prescribe an eye ointment or eye drops. You will need to put these into your cat’s eye(s) daily for 1-2 weeks. If your vet suspects a bacterial infection, such as Chlamydia, they may prescribe both antibacterial eye drops and an oral antibiotic.

If they suspect a viral infection, such as Feline Herpes Virus, they will prescribe anti-viral eye drops. They may also prescribe a supplement, called L-Lysine, that can decrease the ability of the virus to replicate.

Finally, if they suspect the conjunctivitis is due to allergies or an irritant, they may prescribe an anti-inflammatory eye drop and to flush your cat’s eye out with eye flush.

For the most part, as long as you administer the eye medication as directed, the conjunctivitis should typically resolve within 1-2 weeks. That being said, if your cat’s eye issue is due to an irritant or allergy and they are constantly being re-exposed to the inciting factor, the conjunctivitis can return.

Try to keep your windows closed and limit their access to the outdoors. Unplug any air fresheners, do not burn candles, and try to limit the use of any air freshener sprays as these could be contributing to your cat’s eye problem.

More Extensive Diagnostics

If your cat’s eye problem isn’t improving with the above treatments, your vet may recommend taking a biopsy of your cat’s conjunctival tissue. Taking a biopsy will involve your cat being put under anesthesia and your vet cutting out a small piece of the conjunctiva.

They will then send the piece of tissue to the lab for it to be evaluated by a pathologist under the microscope. This will provide information regarding if the eye issue is due to a certain type of cancer versus a rare infection or something else.

Another test your vet can do is a bacterial culture of the conjunctiva. If the conjunctivitis is not improving with the typical antibiotics, then sending in a sample of the discharge to be cultured is helpful.

Taking a culture is very simple. It involves your vet using a swab similar to a Q-tip to gently rub the conjunctiva of your cat to obtain some of the material.

The swab is then sent to a lab, where they will allow the bacteria to grow in petri dishes. The lab can identify exactly what bacteria is causing the problem and what antibiotics it is susceptible to.

How to Administer Eye Drops in Cats

This can be very tricky and sometimes a frustrating process. It would be best if you had someone who could help you in this process, but many people understandably have to attempt it alone.

If you have someone to help you, have one person hold or restrain your cat. Once your cat is still and their head is stabilized, the other person can apply the eye drop or ointment into the affected eye(s).

They can use their index finger and thumb to gently separate and open your cat’s eyelids and then administer the eye meds as directed by your veterinarian.

If you are putting the eye meds in by yourself, try these steps:

  • Hold your cat in close to your body with their rear end pressed up against your stomach. This is so they cannot wiggle away. It is best if you do this sitting down on the floor or in a chair.

  • With your non-dominant hand, hold their head with your thumb on top of their head and the rest of your fingers underneath their chin. This allows you to control the movement of their head and lift their head up so their eyes are looking up to the ceiling.

  • If your cat is very wiggly and will not sit still, you may need to use your non-dominant hand to hold their scruff. This is a good way to control the movement of your cat and make the process easier on you. Do not worry- it does not hurt your cat! It keeps them calm and still.

  • Now, use your dominant hand to put in the eye meds. If you are scruffing your cat, their eyes are likely fully open so you should not need to hold their eyes open.

  • If you are holding their head in your hand, you may need to use your thumb, which is on top of their head, to gently pull up and back on their upper eyelid if their eye is closed or squinting.

If using an ointment, gently rub your cat’s eyelids over their eye after you apply the ointment. This will get it to move around and be dispersed. Try not to directly touch the surface of their eye with anything- not your finger or the eye medication bottle.

It is also a good idea to wash your hands both before and after application of the eye meds. This ensures you are not inadvertently putting any germs in your cat’s eyes. It also removes any antibacterial or other residues from your hands afterward.


If my cat has conjunctivitis, are they contagious to other cats?

Depending on the cause of the conjunctivitis, yes. If your cat has a bacterial or viral infection, yes, they can be contagious to other cats. It would be best to keep them separate from other cats in the home until their signs have resolved.

Although, by the time they are showing symptoms, it is likely they have already spread the infection to other cats they are in close contact with often.

Can conjunctivitis resolve on its own?

In some cases, yes. Depending on the underlying cause and severity, some cats can get over their conjunctivitis on their own without ever needing to see a vet or get medications.

However, this is not the case for all cats and it is always best to schedule an appointment with your vet to prevent any long-term eye problems from developing. Do not wait any longer than 1-2 days to see a vet.

Are their eye specialists for cats?

Yes! There are in fact veterinary ophthalmologists who specialize in eye conditions in cats! If your cat’s eye issue turns into a chronic problem and your vet cannot get it under control, they may refer you to a veterinary ophthalmologist for specialized care and best outcomes for your cat.


Conjunctivitis can be caused by many different things. It can be self-limiting for some cats and a long-term chronic problem for others. While it is okay to wait a couple of days to see if your cat’s conjunctivitis goes away on its own, go ahead and schedule an appointment with your veterinarian just in case it sticks around.

You can always cancel the appointment if things get better. However, if the conjunctivitis is allowed to get worse, it could affect your cat’s vision and the long-term health of their eyes.

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