What Is a Cat’s Third Eyelid & What if It’s Showing? Vet Approved Advice

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.
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.
Health Conditions That Cause the Third Eyelid to Protrude:
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.
Alarming Signs to Watch Out For:

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.
Sources
Featured Image Credit: Antoniya Kadiyska, Shutterstock
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Codee Chessher is a freelance writer with extensive knowledge on a variety of subjects that include travel, DIY, pets, and more. He has a colorful past but the written word was always his first love. He believes there's nothing a well-worded sentence can't accomplish!
When not writing, Codee enjoys reading fantasy novels, tackling DIY projects around the house, and memorizing useless pop culture trivia. He has lived in many places around the US, and most recently resides in northern Mexico.













