What the Heck is Eye Gunk, Anyway?

And why does so much of it crust up in our peppers when we’re asleep?


Most of us wake up in the morning and proceed to wipe away our eye gunk without stopping to think: What is this stuff? Where does it come from? And why does it mostly only come about when we’re asleep? Dr. Andrea Thau, optometrist and president of the American Optometric Association, helped us get to the bottom of all these crusty questions.

For starters: Eye gunk is a type of rheum, a watery fluid that’s naturally discharged from our eyes, noses and mouths. “It’s a combination of mucus, oil, skin cells and other debris that accumulate in the corner of our eyes while we sleep,” Thau explains. “It also has a protective function: Removing waste products and potentially harmful debris from the tear film and the front surface of your eyes.” Which we should all be thankful for, since as Thau adds, the eyes create a dark, warm and moist environment—the perfect home for bacteria to grow.

When we’re awake, the rheum is constantly pushed aside whenever we blink—our eyelids corral it down to our tear ducts, where it’s washed away before it has the chance to harden in the corners of our eyes. When we’re asleep, however, we’re not blinking, so the rheum builds up and turns into that crusty stuff covering your eyelids each morning.

While rheum isn’t a problem for most people, Thau warns that if your eyes are leaking day in and day out, it may be a symptom of more serious medical conditions, like blepharitis, blocked tear ducts or conjunctivitis (aka, pink eye). She adds that it’s a good idea to have your eyes checked if the gunk is accompanied by any of the following symptoms:

  • Redness in one or both eyes
  • Thick discharge that makes your lids stick together
  • A gritty or sandy feeling in one or both eyes
  • Itching or burning sensation in one or both eyes
  • Excessive tearing
  • Swollen eyelids
  • Increased sensitivity to light
  • Blurred vision
  • Pain

If your eyes aren’t stinging or glued together by the stuff, though, simply enjoy the satisfaction of wiping that crust away each morning, and thank it for keeping your eyes safe and healthy.