TikTok Explains What the Yellow Crust in Your Eyes Upon Waking Up Really Is

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eye closeup with faint wrinkles

Eye crust, sleepies, eye boogers — when you wake up, rub your eyes, and find a collection of yellow crust, just what is it? This common morning phenomenon apparently intrigues many, as shown by a viral reaction to an Andrew Huberman TikTok on the topic. But what exactly is it?

“If you have ever woken up in the morning and you have some crust on your eyes… And you know that crust, that kind of yellowy stuff, sometimes it’s yellow, I know this is kind of gross,” says Huberman, bracing the audience in the video, which is no longer available on TikTok (1). 

What Is Eye Gunk?

“That’s actually dead bacteria that your eyes have successfully defeated during your night’s sleep,” Huberman reveals in the TikTok clip.

Like most strange and wonderful bodily secretions, eye gunk has a formal name — rheum. According to Dr. James Kelly, an ophthalmologist, refractive surgeon, and owner of the Kelly Vision Center in New York, NY, rheum is a fancy term for eye discharge. It’s an unsavory cocktail of mucus, oil, skin cells, and other debris your eyes naturally produce and shed throughout the day.

Causes of Morning Eye Crust

Your body constantly works to keep you healthy and maintain balance, and the eyes are no exception. According to Dr. Kelly, eye crust formation is actually part of our body’s defense mechanism against bacteria. 

Eyes have what’s called a ‘tear film,’ which is a thin layer of moisture covering your eyes and acting as a protective shield against dust, debris, and bacteria. “This discharge traps and expels foreign particles to protect the eye as part of the body’s defensive mechanism against germs,” adds Shonit Jagmohan, Director and Optometrist at Vision Camberwell in Australia.

In fact, some components of the tear film have antibacterial properties. “For example, lysozyme can actively kill certain bacteria, providing a chemical defense against infection,” says Kelly. When awake, blinking helps to spread the tear film across your eyes’ surface, then clears this discharge away into the tear ducts. 

As you sleep, your eyes continue to produce this tear film, which traps any unwanted guests, but since blinking stops, mucus sits in the corners of the eyes and along the lash line, where it can dry out and become more concentrated. The result is a crusty souvenir waiting for you in the morning — your eyes’ way of doing a little housekeeping while you sleep.

If you tend to find an accumulation of eye crust more often than not, it could be due to extra oils from the eyelids, skin cells, and potentially accumulated dust or makeup particles. “This is why it is important to wash off makeup thoroughly if you are wearing it,” says Kelly.

What Does Eye Crust Indicate About Eye Health?

According to Huberman and Kelly, while gross and slightly annoying, eye crust is actually a sign that your eyes are doing their job. The presence of eye crust is a testament to your eyes’ self-cleaning and protective processes. 

This crust is a sign that your eyes are effectively trapping and removing potential irritants and harmful bacteria. “So when you wipe those away, you’re taking the casualties of a war that you won during your night’s sleep, and you’re whisking those away,” explains Huberman.

However, while a bit of morning crust is a sign of healthy eyes, there are times when it might be a cause for concern. According to Dr. Jagmonan, changes in the amount, color, texture, or consistency of your eye crust could be a red flag. Dr. Kelly also warns that any redness or soreness is a cause for concern. For instance, if you’re waking up with your eyes practically glued shut, it might be a sign of conjunctivitis, also known as pink eye. 

Excessive crust could also indicate blepharitis, which is an uncomfortable inflammation of the eyelids. Dry eye syndrome, corneal ulcers, and blocked tear ducts can also increase eye crust. 

Morning crust is often a sign of your eyes doing their nightly clean-up, but if you notice any unusual changes, it’s best to alert your doctor. Some underlying reasons for unusual eye crust, such as corneal ulcers, are rare but often lead to red, painful eyes. This is a medical emergency, as it can lead to vision loss, according to Kelly.

How to Clean Eye Crust

Cleaning eye discharge safely and effectively is essential for maintaining eye health. Dr. Jagmohan says, “Use a moist towel to gently wipe the discharge, moving from the inner to the outside corner of the eye, in order to preserve eye health, and don’t rub your eyes too hard.” 

Additional advice from Dr. Kelly includes:

  • Wash your hands frequently
  • Clean your eyes with a doctor-recommended gentle cleanser
  • Use clean towels and avoid harsh objects near your eyes
  • Rinse your eyes regularly
  • If you wear contacts, remove and clean them regularly
  • 1. Nair, Joshua. “People mind-blown after discovering what yellow ‘sleep’ in eyes when you wake up actually is,” LadBible; https://www.ladbible.com/entertainment/tiktok/yellow-crust-eyes-sleep-explained-tiktok-840643-20240118; January 18, 2024.

  • Kelly, James. Author interview. January 2024.

  • Jagmohan, Shonit. Author interview. January 2024.

Rachel MacPherson

Rachel MacPherson

Rachel MacPherson, BA, is a CPT, Certified Strength and Conditioning Specialist, Certified Exercise Nutrition Specialist, Certified Pre/Post-Partum Fitness Trainer, and Pain-Free Performance Specialist. She's passionate about providing readers with straightforward, actionable tips to make living an active, vibrant, fulfilling life easier. When she's not writing, you can find her lifting heavy things, reading, exploring outdoors, or watching the newest iteration of the Star Wars Universe. She lives with her family and pets in beautiful Nova Scotia, Canada.

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