Cat Third Eyelid Showing – Causes and Treatments

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Lots of people get frightened when they see their cats suddenly have third eyelid showing. They haven’t known that this is a common condition in cats, due to various causes. Cat third eyelid showing may be quite normal and doesn’t need any special treatments, but it can be a sign of cancer which needs the special help from vets. So, let’s get more information about it.

What Is the Third Eyelid?

The third eyelid (also called nictitating membrane, plica semilunaris or palpebra tertia) works as an extra protective layer of the eyes. It’s quite thin and has the color of white or light pink. Normally, a third eyelid is large enough to cover all the eyeball, which has the function of moistening and protecting animals’ eyes from dirt and injuries.

Normally, we cannot see the cat third eyelid because it stays deep inside their eyes. But in some situations, like while the cats are snoozing or relaxing (they don’t close their eyes entirely), you can see it. Or when the cats are alert, a small portion of the third eyelid will expose, which allows us to see it.

Cats are not the only animal that has this special feature, but birds, dogs, lizards and camels have this as well.

What Cause Cat Third Eyelid Showing?

Generally, the third eyelid doesn’t protrude out except some situations that I mentioned above. So, if you see your cats whose third eyelid show up abnormally, you should watch out because they may have injured after a fight with other cats or they are getting a disease.

However, some kittens are born with this condition at first. In this case, cat owners also need to notice.


Photo credit: Stef Noble 

The most common reason for cats’ eyes injure is fighting (just like eye watering in cats). Cats fight for many reasons like fighting for territory, for female cats or just because of being aggressive.

After a fight, they may get an injury somewhere in their body, including the eyes. As an automatic mechanism of the body, the third eyelid will appear to cover the cats’ eyes to protect it.


Getting cancer may be a reason for the third eyelid showing. Due to exposing to the sunlight regularly, white cats and outdoor cats are more likely to get this than others.

Haw’s Syndrome

Haw’s syndrome is the condition in which the third eyelid in the corner shows longer than normal. Cats getting this syndrome usually don’t have any problems with their health or their vision. They can grow up completely normal like any cats.

There are several reasons that can cause haw’s syndrome, including:

  • Parasites
  • Cat flu
  • Fatigue
  • Viral infections

Horner’s Syndrome

This is the condition in which the sympathetic nervous system in cats have problems. This system warns to the sympathetic nerves that the eyes get wounded. As a result, the eyelid appears to protect the eyes although they don’t get any injuries.

Photo credit: Marty McKee 

The causes of this syndrome in cats are identified. The cats may be hit by vehicles or bite by other animals in the neck, ear or eye area that affect the nerves in these areas. On the other hand, there’re several other reasons:

  • Eye diseases
  • Tumors (in the neck, chest or brain)
  • The middle ear infection


A serious dehydrated cat will expose their third eyelid outside their eye corner. You definitely recognize this situation in cats because they properly look unwell. In this case, you should take your furry balls to the vet as soon as possible because every effort rehydrating them now is useless.

Treatments for Cat Third Eyelid

In fact, most of the getting accident and cause will resolve by their own over time, no need for the help of the vets. The vets just help to heal the wounded faster. You can also help your cats heal the injuries faster by using eye drop or antibiotic (in case the wound is too big and can’t heal by itself).

In case your cats have cancer, only the professional vets can decide what will the best option to cure your cats. In general, there’re two common options: surgery and radiotherapy. No matter what the choice is, all of them have the same purpose: to remove the cancer tumors.

Cats getting Haw’s syndrome are the ones that cat owners shouldn’t worry about. This condition will disappear by itself if you eliminate the reasons causing it.

Like Haw’s syndrome, cats with Horner’s syndrome either need to be worried about. But in some circumstances, the vets will treat them with phenylephrine drops. This also depends on how worse is your cats’ condition.

In case your cats get dehydrated, the first thing to do is giving them more water and wet or soft food so that it can improve the condition. Then, take them to the vets immediately to make sure your furry friends get the best treatment.

You may not know this, but there are some kittens have third eyelid protrusion already. This is because of the genetic problems. If you notice some of your newborn kittens having an eyelid that covers all their eyeball, you must take them to the vets right away. The vets will give them surgery to bring the membrane back to the place it must be.

Risks of Cat Third Eyelid

Not all of the cats that have strange eyelid need to be treated. However, in general, because most of them have problems with their health and nerve system, they must be cured by the vets on time.

If not, the worst situation is that they will lose their vision forever. But you should not too worry about this case because it rarely happens.


In general, third eyelid showing in cats may be just a normal injury, but it can be a sign of getting cancer. No matter what the reason is, you should show your responsibility by taking them to the vets on time. Don’t think that it’s just a simple situation because if you’re too late, your cats can die of serious cancer or be blind forever.

Now, you know some important facts about cat third eyelid showing. If you have any questions, just leave them below, we will answer them as soon as we can. Thanks for reading!

Comments (1)

  • My cat has been bitten by a brown dog tick which I have since removed but 3 days later his third eyelids are still showing although he is showing no signs of another abnormalities.

    Should he visit the vet or will there recede on there own?


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