Grey cat with yellow eyes

You might notice your cat's third eyelid showing when they blink, yawn or wake up.

© Nils Jacobi - Shutterstock

Why is my cat's third eyelid visible?

By Dr Jo de Klerk, BVetMed (Hons) MScTAH MRCVS Veterinarian

Updated on the

Stress, tiredness and ill-health can all lead to a cat's third eyelid appearing. Here's what to do if that happens.

The third eyelid is also known as the nictitating membrane. Humans do not have a third eyelid, but cats and many other animals do. Its role is to protect the outer layer of the eye and keep the eye moist.

Most of the time, it is not visible, as it retracts into the inner corner of the eye. But when your cat is unwell or has a problem with their eye, it becomes visible. This is an indication that you should take your cat to the vet.

What does a cat's third eyelid look like?

A normal third eyelid is not easily visible. Yet you might occasionally notice it when your cat blinks, yawns or wakes up from a deep sleep.

A third eyelid is a conical shaped film in the inner corner of your cat’s eyes. It is very thin and usually has a dark rim around it. The most inner part is usually a very pale pink or white colour. If it is red, this is abnormal.

What do you do when your cat's third eyelid is showing?

If your cat’s third eyelid is showing, you should take them to a veterinarian for a check over. Primary eye conditions, particularly trauma, can progress quickly and can cause serious consequences if left untreated. If your cat doesn’t have a primary eye condition, they will also need treatment for the condition that is making him feel unwell.

Why does my cat have a third eyelid visible in one eye only?

If your cat only has one of their third eyelids showing, it is usually an indication that the problem is with that specific eye, rather than general ill-health.

Trauma to the eye, such as an object in the eye, a scratch, a corneal ulcer or a foreign body in the eye can cause this. Or it could be an infection that has not yet infected the other eye.

Eye injury is serious, therefore it is important that you take your cat to the veterinarian for investigation. Eye conditions are painful and can be serious. They can rapidly lead to vision problems or even blindness if left untreated.

Why are my cat's third eyelids visible in both eyes?

If your cat’s eyes both show their third eyelids, this is an indication that there is either a problem with both eyes or your cat is generally feeling unwell. Eye infections, such as conjunctivitis (also called pink eye), tend to affect both eyes at the same time. Internal eye problems, such as glaucoma, can also cause the third eyelids to protrude.

Having said that, it may not be a problem with the eyes. Any ill-health that causes a fever and general malaise can result in the third eyelids protruding. This is particularly common for cat flu infections.

Cat with third eyelid showing ©Kristi Blokhin - Shutterstock

Why are my cat's eyelids red?

If your cat’s inner eyelids (conjunctiva) are red, this means they are inflamed and sore. This is known as conjunctivitis. Conjunctivitis is usually caused by a bacterial or viral infection. Yet trauma can also be a trigger, and requires treatment by a veterinarian.

Can you see a cat's inner eyelid?

In a normal cat, you will struggle to see the third eyelid. You might see it protract slightly when your cat blinks, yawns or when they first wake up. Straight after, it should go back to the normal position in the inner corner of the eye.

Why is my cat's third eyelid showing and they have diarrhoea?

The third eyelid can show due to any feeling of ill health. But a condition known as Haw’s Syndrome can cause diarrhoea and third eyelid protrusion in cats. Much is unknown about it, but it has been speculatively suggested that it is associated with either tapeworm or intestinal viral infections in young cats. Most of the time it is mild and cats recover with supportive treatment from their veterinarian over the course of several weeks.

Why is my cat's third eyelid showing and they are lethargic?

When your cat is unwell, their third eyelids may protrude and they may act lethargic. It is unknown why the third eyelids protrude. Yet it is thought to be because there is a dysfunction in the nerves that tell the third eyelids to stay in place. If your cat is lethargic and has protruding third eyelids, you should take your cat to the vet, as there are many potential causes that need treatment.

Someone is relaxing today! ©Andi111 - Shutterstock

Why is my cat's third eyelid showing and they are sneezing?

Upper respiratory tract infections can cause third-eyelid protrusion and sneezing. These infections can be part of the ‘cat flu’ complex. You should take your cat to the vet, if they are showing these signs, as cat flu can have serious consequences if left untreated, both in the short-term and over the lifetime of your cat.

Why is my cat's third eyelid showing but they're showing no other symptoms?

There are many reasons why your cat’s third eyelids might be showing, even when you do not notice other symptoms. If your cat has just woken up from a deep sleep, wait some time to see if the third eyelids retract. Yet if they stay visible, your cat needs a visit to a veterinarian to investigate why the eyelids are protruding. There may be a corneal abrasion, an underlying health condition or eye condition that needs to be treated.

Is my cat's third eyelid due to stress?

Stress in itself does not cause the third eyelids to protrude. What may have happened is that cat flu can be caused by viruses that stay latent in the body.

At times of stress, the virus becomes active again and causes ill health and third eyelid protrusion. Therefore, if your cat has had an episode of cat flu before, you should try to keep their environment as stress-free as possible, through the use of pheromone diffusers and making a conscious effort not to make drastic changes to their living environment.

Why is my cat's third eyelid swollen?

If your cat’s third eyelid is protruding and seems swollen, this might be a condition known as cherry eye. Cherry eye is more common in dogs than cats, yet certain breeds, such as the Burmese, are prone to it.

There is a gland in the third eyelid and when this becomes swollen, it turns the third eyelid inside out. This interferes with the function of the third eyelid. Medical management with eye drops is rarely successful and most cases need to be surgically repositioned.

Why is my cat's inner eyelid stuck?

If your cat’s third (inner) eyelid is stuck in an outward position, this means that there is something wrong with your cat. Your cat might be feeling unwell or they might have a primary problem with the eye. There are many causes and you should visit a veterinarian for your cat to have a check over.

When should I see a vet?

If your cat’s third eyelid in one or both eyes is visible and doesn’t retract back to its normal position, your cat needs to be clinically examined by a veterinarian. They may need treatment for the eye or for ill health. There are many causes of visible third eyelids and, left untreated, many of them can have serious consequences.

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