Cats Third Eyelid Showing Causes And What To Do

Cats have a unique anatomical feature most pet owners rarely see—the third eyelid, also known as the nictitating membrane. Located in the inner corner of each eye, this thin, pale tissue normally remains hidden, only emerging briefly to sweep across the eye for protection or moisture. When it stays visible, however, it can signal an underlying issue. Persistent third eyelid protrusion is not normal and should never be ignored. Understanding why it happens and how to respond can make a critical difference in your cat’s comfort and long-term health.

Anatomy of the Feline Third Eyelid

The third eyelid serves several protective functions. It produces part of the tear film, helps remove debris from the surface of the eye, and acts as a shield during injury or sleep. Unlike humans, cats—and many other animals—retain this evolutionary adaptation. The membrane contains a small amount of cartilage for structure and is rich in lymphoid tissue, contributing to immune defense in the eye area.

Under healthy conditions, the third eyelid retracts completely when the eye is open and active. It may flicker into view momentarily when a cat blinks rapidly or is drowsy, but prolonged visibility is a red flag. Because the third eyelid lacks pigmentation, it often appears pale pink or white, making it noticeable against the darker iris and sclera.

Common Causes of Third Eyelid Protrusion

Several factors can cause one or both third eyelids to remain exposed. Some are mild and temporary; others point to serious illness. Key causes include:

• Eye irritation or injury: Foreign bodies, scratches, or inflammation (conjunctivitis) can trigger the membrane to cover the eye partially for protection.
• Infections: Viral infections like feline herpesvirus or bacterial conditions such as chlamydia can lead to swelling and third eyelid emergence.
• Haw’s Syndrome: A condition specific to cats where both third eyelids protrude due to intestinal parasites or gastrointestinal upset, especially in younger cats.
• Dehydration or illness: Systemic diseases causing lethargy, weight loss, or dehydration can result in sunken eyes, allowing the third eyelid to show.
• Neurological issues: Damage to the nerves controlling eye muscles—such as Horner’s syndrome—can impair retraction of the third eyelid.
• Tumors or growths: Masses behind the eye or within the eyelid itself may physically push the membrane forward.

Tip: Observe whether one or both eyes are affected. Bilateral involvement often suggests systemic illness, while unilateral cases may point to localized trauma or nerve damage.

When to Be Concerned: Red Flags

Occasional, brief appearance of the third eyelid is not alarming. But if it remains visible for more than a few hours, especially with other symptoms, veterinary evaluation is essential. Warning signs include:

• Prolonged exposure of the third eyelid
• Squinting or excessive blinking
• Discharge (watery, mucous, or pus-like)
• Cloudiness or changes in eye color
• Lethargy, appetite loss, or vomiting
• Visible injury or swelling around the eye

“Persistent third eyelid elevation is a clinical sign, not a diagnosis. It tells us something is wrong—but finding the root cause requires a thorough exam.” — Dr. Lena Reyes, DVM, Feline Ophthalmology Specialist

Diagnostic Process and Veterinary Evaluation

A veterinarian will begin with a physical examination, focusing on ocular health and overall condition. Diagnostic steps may include:

1. Eye stain test: Fluorescein dye checks for corneal ulcers or scratches.
2. Schirmer tear test: Measures tear production to rule out dry eye.
3. Neurological assessment: Evaluates facial symmetry, pupil response, and nerve function.
4. Fecal examination: If Haw’s Syndrome is suspected, testing for intestinal parasites is crucial.
5. Blood work or imaging: For systemic illness, blood panels, X-rays, or ultrasound may be needed.

In some cases, referral to a veterinary ophthalmologist may be necessary, particularly if tumors, deep infections, or complex nerve disorders are suspected.

Step-by-Step: What to Do If Your Cat’s Third Eyelid Is Showing

If you notice your cat’s third eyelid is visible, follow these practical steps:

1. Observe closely: Note duration, frequency, and whether one or both eyes are involved.
2. Check for other symptoms: Look for discharge, squinting, changes in behavior, or digestive issues.
3. Avoid self-treatment: Do not apply over-the-counter eye drops or attempt to remove foreign objects.
4. Minimize stress: Keep your cat in a quiet, dimly lit space to reduce discomfort.
5. Contact your vet: Schedule an appointment promptly, especially if symptoms persist beyond 24 hours.

Cause	Typical Signs	Action Required
Haw’s Syndrome	Both third eyelids visible, no pain, possible recent diarrhea	Vet visit, fecal test, supportive care
Conjunctivitis	Redness, discharge, squinting, one or both eyes affected	Antibiotic or antiviral treatment
Corneal Ulcer	Pain, tearing, sensitivity to light, cloudiness	Immediate veterinary care
Horner’s Syndrome	One-sided drooping eyelid, constricted pupil, raised third eyelid	Neurological workup
Dehydration	Dry gums, lethargy, poor skin elasticity	Fluid therapy under veterinary supervision

Mini Case Study: Bella the Kitten

Bella, a 5-month-old domestic shorthair, was brought to her vet after her owner noticed both third eyelids were clearly visible for two days. The kitten wasn’t squinting or producing discharge, but she had experienced mild diarrhea the week before. After a physical exam and negative fluorescein test, the vet diagnosed Haw’s Syndrome. A fecal sample revealed roundworms. Bella was dewormed and monitored at home. Within ten days, her third eyelids had fully retracted, and her digestion normalized. This case highlights how gastrointestinal health can directly impact ocular signs in young cats.

Prevention and Long-Term Eye Care Tips

While not all causes of third eyelid protrusion are preventable, proactive care reduces risk:

• Keep vaccinations up to date to protect against feline herpesvirus and calicivirus.
• Use regular parasite prevention for both internal and external worms.
• Monitor eye health weekly during grooming sessions.
• Avoid exposing cats to smoke, dust, or strong cleaning chemicals.
• Provide clean water and a balanced diet to support immune function.

Tip: Use a damp cotton ball (with plain water) to gently wipe away minor eye crusting. Always wipe from the inner to outer corner to avoid pushing debris toward the tear duct.

FAQ

Is it normal for my cat’s third eyelid to show when sleeping?

Yes, brief visibility during deep sleep or relaxation is normal. However, if it remains exposed when your cat is awake and alert, further evaluation is recommended.

Can stress cause the third eyelid to appear?

Indirectly, yes. Severe stress can suppress the immune system, increasing susceptibility to infections that affect the eyes. Stress alone is unlikely to cause prolonged protrusion without another underlying factor.

Do all cats have third eyelids?

Yes, all cats have third eyelids. It’s a natural anatomical feature present in most mammals, though it’s more developed and functional in carnivores and birds.

Conclusion: Act Early, Protect Your Cat’s Vision

The appearance of your cat’s third eyelid is more than a curious quirk—it’s a potential window into their overall health. Whether the cause is minor irritation or a deeper systemic issue, timely attention prevents complications and preserves ocular function. Never assume the problem will resolve on its own. With proper veterinary care, most conditions leading to third eyelid protrusion are treatable, especially when caught early.

💬 Your observations matter. If you’ve noticed changes in your cat’s eyes, share your experience or questions below—your insight could help another pet owner act sooner.