People Are Surprised to Learn What That ‘Sleep Crust’ in Your Eyes Actually Is

We’ve all experienced waking up with sleep crust in our eyes at some point. You know the stuff: The yellow-ish, crusty stuff in the corners of your eyes when you wake up. We might not have given it much thought when we rub our eyes and see those white or yellowish sticky substances. However, this eye gunk, commonly known as sleep crust or ‘sleep’, actually holds interesting insights into our eye health. This is what sleep crust is, how it forms, and its implications for our eye health.

What is Sleep Crust?

It turns out that while we sleep, our eyes are fighting a battle. That’s right: A battle against bacteria and other unwanted, microscopic stuff. The crust in our eyes is the result of our eyes winning that battle. So, you could say that the yellow crusty stuff is kind of like a trophy of a battle fought and won while you slept. But what is this eye gunk really made of, and why is it yellow?

Sleep crust, known medically as “rheum,” refers to the combination of mucus, oil, skin cells, and debris that accumulate in the corners of our eyes during sleep. Despite its less glamorous appearance, sleep crust serves an essential purpose in our body’s natural self-regulating cleaning system.