Cats have a unique anatomy. For instance, did you know that cats have not one or two eyelids, but three? It’s true! A cat’s third eyelid is technically called the nictitating membrane, located in the inner corner creases of your cat’s eyes. This eyelid serves an important function: producing and spreading a uniform tear film on your cat’s eyes using the tear glands. It helps them shrug off getting some dirt in their eyes as well as keeping the eyes hydrated, which are both important on the prowl. Lastly, it helps prevent infection in the eye.
You probably know about the regular top and bottom eyelids we share with cats—they protect the delicate eyes from harsh UV rays, dirt, dust, infection, wind, water, and other environmental hazards. Eyelids also lubricate the eyes and wash away most irritating particles before they can scratch the cornea. But what about if your cat’s third eyelid is showing with no other symptoms? Is that serious, or does it happen normally? It could be either, to tell the truth. Let’s dig in to find out normal times for when your cat’s inner eyelid is showing, as well as when to be worried and consult your vet.
Is It Bad for My Cat’s Third Eyelid to Show?
No, it’s not necessarily bad for your cat’s third eyelid to show by itself. It may appear to protrude a little when your cat is very relaxed or sleepy, and it can also make an appearance when cats undergo anesthesia. These are both perfectly normal and a result of muscle relaxation. The third eyelid may also show when your cat is dehydrated, so make it your first order of business to top up their water bowl and consult with a veterinarian before trying to diagnose more insidious health problems.
If you have a question about your cat's health or behavior, why not Ask a Vet for Free with Catster. Our veterinary team answers reader questions and provides trusted advice to help you better understand your cat.
Potential Causes of a Protruding Third Eyelid
It can also be a bad sign when the third eyelid becomes visible. More specifically, it can signify an ocular condition, or even another health condition that is unrelated to your cat’s eyes.
When the third eyelid protrudes or appears to prolapse outward, you should take your cat to the vet. It’s possible they have one of several health conditions.
- Cherry eye: This dramatic-looking condition causes the third eyelid’s lacrimal (tear) gland to slip out of place and protrude outward. This condition isn’t usually painful in cats but can herald later ocular issues if untreated.
- Conjunctivitis: Also known as pink eye, this painful eye infection causes inflammation on and around the eye and oftentimes makes the third eyelid protrude.
- Corneal ulceration: Ulceration occurs when the epithelium, or outer layer of the eye, begins losing cells due to a wound, injury, or foreign contaminant. This can progress into ocular perforation or holes in the eye if left untreated.
- Fever: High fevers from infections can dehydrate your cat’s body and can cause the third eyelid to jut outward.
- Nerve damage: Nerve damage in the neck or face can cause protrusion of the third eyelid. It typically affects only one eye and can also affect the size of the pupil and muscle movement on one side of the face.
- Glaucoma: Caused by fluid building up in the eye, glaucoma can push the third eyelid out to become more prominent.
- Upper respiratory infections: Commonly caused by certain viruses, respiratory infections can result in inflammation that presses the third eyelid outward.
- Haws syndrome: Haws syndrome is characterized by the protrusion of both third eyelids. The cause is unknown, but it is often related to inflammatory issues in the digestive tract.
When to Worry About Your Cat’s Third Eyelid
While it’s normal to see the third eyelid when your cat is relaxed or sleepy, you shouldn’t be seeing it every day. When accompanied by a few telltale signs, you can more exactly pinpoint what the cause could be. If your cat’s third eyelid is showing and they exhibit any of the following signs, visit your vet immediately.
- Discharge from the eyes
- Persistent redness or inflammation
- Squinting
- Pawing at the face or eyes
- Fatigue or lethargy
- Changes in appetite
Final Thoughts
It’s normal to see your cat’s third eyelid when they’re relaxed and sleepy. However, if you see the third eyelid protruding along with eye inflammation, pawing at their face, or other concerning signs, your cat might have a more serious condition, like conjunctivitis. Take your cat to the vet as soon as you notice these problems occurring to prevent them from becoming more serious later.
Featured Image Credit: Antoniya Kadiyska, Shutterstock
Is It Bad for My Cat’s Third Eyelid to Show?
12 Responses
We have a 4 month old stray kitten – her left eye had tons of white, thick drainage. We took her to the vet, antibiotic injection given… was a bit better for a few days, now still with some drainage (although no where's near as much as there was)… she used to open that eye every so often but now she's not opening it… she's bubbly and bouncy and happy, eating like a horse. She also has very soft stools ever since we've had her.
Hi Nancy, thanks for sharing your story. Perhaps consulting your vet would be ideal to find out if she needs further treatment? If that is not possible for some reason, you can always have a chat with one of our vets at www.pangovet.com. While they can not prescribe a medication, they can help you narrow down the possible causes, understand the urgency and next best steps, as well as give you some great care tips.
my mainecoon has suddenly as I can see a third eyelid it's only quarter of an inch but 2 days he's eating playing but I'm so worried he did eat half a catnipball 2 days ago. should I be worried can't stop crying he's only 1
Hi Alison. Sorry to hear about your Maine Coon, you can request a 1:1 call with Dr. Marta at www.pangovet.com she is a veterinary ophthalmologist and can support you in clearing up any questions to help determine the urgency of your cat's case. Best luck!
I have a 5 yr old neutered medium long haired black cat. He has had the third eyelid showing since he was probably a year old if not sooner. Rescued at 8 months old. He was examined by a vet, who had said what the condition was. Also, said not to worry unless it seemed to start bothering him. But now, after reading this information, I’m wondering if I should worry.
Hi Keeno,
Thank you for your comment and for sharing your cat's history. It’s natural to feel concerned after reading new information, especially when it comes to our beloved pets. Since your veterinarian has already assessed the condition and advised you, it sounds like you have a good foundation.
However, if you have any lingering doubts or if the situation changes, seeking additional guidance can be helpful.
We recommend considering an online consultation with a veterinarian through Pangovet.com. Our platform can connect you with experienced professionals who can provide tailored advice for your cat's specific needs.
If you have any more questions, feel free to reach out!
Best regards
My friend has 2 cats that the 3rd eye lid is covering 1/4 of their eyes, yes both eyes, she took them to vets and don’t know what happened, sent pictures to a eye doctor but they have never heard back from them, the vets are stumped cause they act normal, do you have any idea how to fix this? I have pictures of the cat that has it the worst
Hi Terrie, thanks for getting in touch! There are a few things it could be, and it sounds a bit like Haws Syndrome (see here: https://www.catster.com/ask-the-vet/haws-syndrome-in-cats-vet-answer/ ) but without actually seeing your friend's cats, we can't say for sure. We do have a team of veterinarians that can help with an online consultation, though, so if your friend is interested, she can go to https://pangovet.com/ and schedule a call. Our vets have a lot of experience with this and are ready to help! :)
Thank you very much. My eleven year cat showed me her third eyelid yesterday while sleeping on my chair and I freaked out. I never knew that cats had three eye lids. I feel much better now.
Hi Phyllis – that would have been very spooky to see for the first time. But now you know about it, glad we could help :)
How about seeing the third eyelid all day, every day, but the cat is healthy and acts like a normal cat(plays, sleeps, eats, drinks, repeat)?? We took the cat to the emergency when we first observed that his both eyes showed the condition. His blood work is perfect, other tests they did on him came back normal as well. No one could tell what's the reason for this.
Hi Lenka,
Thank you for sharing your experience and for being so attentive to your cat’s health. It's great to hear that your cat is otherwise healthy and behaving normally.
The third eyelid can sometimes be visible due to various reasons, but since the condition persists, it’s understandable that you’re concerned. If the issue continues or if you notice any changes in your cat's behavior, it might be helpful to consult with a veterinarian again for further insight. You can schedule an appointment at Pangovet.com where one of our veterinary experts can help you to figure out the reason for your cat's condition.
Wishing you and your cat all the best!