Third Eyelid Showing in Cats - Causes and Treatment

By Josie F. Turner, Journalist specialized in Animal Welfare. Updated: July 8, 2018
Third Eyelid Showing in Cats - Causes and Treatment

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Cats' eyes can be truly fascinating for those who take their time to look into them. Not only due to the fabulous combinations of colors, but also due to the unusual behavior of their pupils, which change in size depending on the amount of light in the environment. Their eyes are so well known for their distinctive appearance, reflection spots on roads are known as cat's eyes.

A cat's eye contains a membrane known as the third eyelid. You may have never seen it, as doing so is a sign of a health problem. As such, if you've recently noticed it, you will need to read up on the causes and treatment for a third eyelid showing in cats, its causes and treatment. Fortunately, AnimalWised provides the information to do so. It is a symptom of a heath problem in your cat and should not be ignored under any circumstances.

You may also be interested in: Gingivitis in Cats: Causes and Treatment

What is the third eyelid?

The scientific name of this membrane located in the eyes of several mammals, including cats, is Tertia palpebra, which is also known as the third eyelid or nictitating membrane. It is a tissue located around the cornea, conjunctiva and mucous membrane. Although it isn't commonly spotted, you might notice some secretions between the eye and the outer eyelids when your cat is half asleep.

The role of the third eyelid is to protect the eyeballs from any foreign object and from traumas as a result of a hit or knock. It is also responsible for releasing a liquid, whose antiseptic properties are capable of fighting against the presence of bacteria and microorganisms that could cause disease. However, these protective uses of the third eyelid do not lead to the feline nictitating membrane to show all the time.

If you see that your cat's third eyelid is visible, either in one eyeball or in both, this means that they are in pain or suffering from a condition or disease[1]. Some research suggests that the appearance of this membrane is related to intestinal parasites and digestive problems, whereas others state that if this membrane is visible then the problem is related with the eye itself. In these latter cases, the problem with the cat's inner eyelid could be due to a prolapse[2]. In order for you to have all the information, we will show you the causes that can cause this tissue to appear in your cat's eye.

Third Eyelid Showing in Cats - Causes and Treatment - What is the third eyelid?

Causes of third eyelid showing in cats

If you see that your cat's nictitating membrane is visible in one or both eyes, these are some of the factors that might be causing it:

  • Conjunctivitis: this ocular infection doesn't only cause the appearance of the third eyelid, but is also causes swelling, tearing and lacrimation.
  • Dehydration: when the cat is suffering from a severe lack of water, the appearance of this ocular tissue is a sign of a serious health condition that needs to be treated by a specialist.
  • Wounds: if your cat has suffered a blow or trauma to the face, both of its eyes may have become affected. Take it to the vet straight away.
  • Foreign body: anything that gets into the cat's eyes, whether rubbish, dust or something else will cause this membrane to appear, as it is a mechanism to prevent it from further imbedding into the eyeball.
  • Cancer: it's possible for this small organ to be affected by the formation of cancer cells.
  • Haws syndrome: this name is given to the appearance of the third eyelid when related to an intestinal problem that the cat is suffering from, or has suffered from recently, whether intense diarrhea or the presence of parasites.
  • Genetics: some cat breeds, such as the Burmese, might be prone to suffering a rupture of this membrane inside the eye, which is very uncomfortable for them.

Furthermore, if you see the third eyelid in your cat it is also highly likely that its eyes will start to lacrimate. They will probably try to touch them with their paws owing to the discomfort caused when this membrane is out of place.

As a note, if a cat's inner eyelid is showing in one eye and not the other, it is still a cause for concern. It may imply a problem on one side of the body, but it still means there is an issue which needs resolving. It might be that you see a cat's third eyelid showing in one eye which progresses to both. This implies the progression of one of the causes listed above.

Treatment for a third eyelid showing in cats

Owing to the various reasons that can cause the cat's nictitating membrane to occupy more space in the eye than it should, there are several types of treatment. Such treatment depends on the source of the anomaly.

In the case of dehydration causing your cat's third eyelid showing, you should give the cat plenty of wet food and water in order to halt the process. It is also recommended to take the cat to the vet, as the animal has been lacking water for too long to be treated at home.

In the case of conjunctivitis, wounds, foreign bodies in the eye and cancer, only the vet's diagnosis will be able to determine the next step to follow. They might be prescribed eye drops and other medications in the first 3 problems, depending on the severity. If they have cancer they may be recommended surgery and/or radiotherapy. Only the specialist can decide on the best option to conserve the cat's health and quality of life. As the cat recovers, their inner eyelid should start to retract.

Haws syndrome should disappear by itself, once the intestinal and digestive problems that caused the appearance of the membrane go away. This, in turn, will lead to the nictitating membrane gradually disappearing as the cat returns to health.

When a genetic reason is behind it, the vet will use medical studies to determine whether the cat's inner eyelid membrane is affecting the cat's vision and causing discomfort. If this is the case the vet may also resort to surgery. This process will not to extract their third eyelid, but will put the feline nictitating membrane back into its correct position.

Third Eyelid Showing in Cats - Causes and Treatment - Treatment for a third eyelid showing in cats

If you want to read similar articles to Third Eyelid Showing in Cats - Causes and Treatment, we recommend you visit our Eye care category.


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Merle Manson
My cat is extremely active, playful and eats well. In the last 2 weeks he's shown third eye, when outside it completely disappears. He has always slept a lot during day and often sits with eyes half closed as if he's going to sleep. He's happy, doesn't like me going away from home which I do 3 days a week. He's possessive.
Thank you God bless Merle.
Administrador AnimalWised
Hi Merle,

We cannot diagnose anything here in the comments, only a vet can do that. In saying this, the third eyelid is a symptom of the conditions detailed in the article. If it is showing, it is likely there is something wrong. Even if it is a relatively minor ailment, it can worsen, so the best thing to do is take them to the vet.
The animal
My cat went to the vet today and they said she has herpes in her eye.. Do you know any causes or anything involved with this?
Administrador AnimalWised
Hi Makayla,

Unfortunately, the feline herpesvirus type 1 (FHV-1) is quite common in cats. As with all herpesviruses, the cat cannot get rid of it completely. It will either lie dormant or you can treat the symptoms. Where they got it almost always from another cat. This could be from licking another cat's face, sharing a litter box or even eating from the same dish. Fortunately, it is manageable, so take the vet's advice and your cat can still have a long and happy life.

Here is some more info to provide some background:
Long story short, i have 3 foster kittens, all came with URI and eye infections. All on meds. A week in my older cat stopped eating, drinking and was lethargic. I vrought him to the vet, they gave him fluids under the skin, amoxicilian, some shots at the vet and a blood test, 500bucks later and he was doing better.. now its days later and hes not eating he has had diarrhea from the amoxicillin he threw up yellow this morning and is very lethargic, but not as lethargic as last time. I can see a little bit of his 3rd eye lid. Also two nights ago my 2 adult cats were sitting in the window, when a stray came up and freaked them out. They started hissing and swatting at eachother, and stopped being friendly towards one another. In the morning the grasscutters came and that scares them. Both were in my bathroom cabinet.. also where Frankie, my sick adult cat likes to sleep. I thought that they were back to normal, but when frankie came out before it looked like it was to get away from lilly (his sister). I am tapped out of money. I dont know what to do... the blood test came back with everything normal, and he has been on amoxicillin every day 2x a day 1ml. Today is supposed to be his last day on it, and it will be bc im just about out of his meds. All of the kittens are still on amoxicillin and terramycin for their eyes. They came off of both for about 6 days and one started sneezing again and anothers eye swelled up and i saw her whole 3rd eye lid.. but this was while frankie was on meds. For the most part they have been seperated, the occasional slip happens when one runs through our feet going in and out of the bedroom. So thry have touched noses here and there. The kittens havent had there distemper shots yet, but my 2 are updated on all shots. They never received their nd distemper shots when they were kittens and the vet i brought to a year later said it wasnt a big deal. So now u know everything, please help! I dont have another 500 to give to the vet also we moved into our new apt about months ago. So my question is, is he sick, is it stress, could it be dehydration? is the amoxicilin even working? What should i do?
Administrador AnimalWised
Hi Erin,

Thank you for sharing and we are sorry to hear about your predicament. Unfortunately, as we point out in the articles we can't diagnose anything here in the comments, even with a picture.

You have done the right thing by taking hem to the vet and it seems like it was very necessary. Antibiotics are usually the only treatment for such infections and it is imperative that the full treatment be carried out without any breaks, otherwise they may not be able to properly fight the infection.

It is also important to remember that it takes some time for these antibiotics to work. Symptoms should start to clear, but they won't be gone completely immediately. If the bloods have come back negative, it is a good sign. It could be stress, sickness or dehydration, so ensure they have stressors removed from their environment and that they have access to plenty of water. These are things which should happen regardless.

Wait until the course is completed and trust your vet's advice. If they still show signs of illness, then you won't have much choice but to take them back. However, before you do, you should call the vet and speak to them about what is happening. If you have paid for treatment already, then they should speak to you about follow ups.

If your cat needs further treatment and you can't afford to pay it, then you will have to look into payment plans, emergency care and anything else offered. Also, speak to your local animal shelter. They will be able to offer the best advice and may even have some treatment plans available through them.
Kimberly Westfall
Thank you for all of the great information. It helped me to see that even though my cat seems ok, he needed to go to his Dr. He is now on antibiotics and should be all better soon.
Administrador AnimalWised
Hi Kimberley,

We are glad we were able to help, it's always good to take them to the vet if you are unsure. Hope it clears up right quick!
What if you don't know which if these is the cause. And what if you don't have the money to go to the vet.
Administrador AnimalWised
Hi Bryanna,

We understand that money is a problem for everyone at some time. Unfortunately, as some of these causes of third eyelid problems are infections, the treatment they need is only available from professionals. This is because on a vet can prescribe the right antibiotics given the correct diagnosis. This is why it is imperative for those wishing to adopt a pet to be in the right position to do so.

However, circumstances can change and even those who were once financially able to care for a cat may struggle at another point down the road. In these cases, your best bet is to visit a cat sanctuary or shelter. They will at the very least be able to advise on how to best help your cat in your area. They also may possibly have programs to help people in your situation.

Good luck and we hope this helps!
This site answered more questions than my Vet. Thank you. Here is a picture of my cat, Peepers
Administrador AnimalWised
We’re happy to help anytime Helen!
Tori Folkestad
My cat has had eye irritation for a couple months. I have been in contact with my vet and they said I do not need to bring my cat in for testing or checking. I am getting worried because as of recently I have been noticing his third eyelid showing and he looks like he is in pain. Should I still stay away from the vet, or find another vet who look at my cat?
Administrador AnimalWised
Hi Tori,

Have you mentioned the third eyelid showing to the vet? If they don't know about it, then you should call and mention it. Otherwise, if you don't trust your vet is providing the right level of care, we recommended speaking to another for a second opinion.

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