The yellowish gunk that collects in the corners of your eyes when you wake up—commonly called “sleep,” “eye boogers,” or “eye discharge”—is a normal part of your body’s nightly maintenance process. According to neuroscientist Andrew Huberman, this material is made up of a combination of mucus, natural oils, dead skin cells, and even dead bacteria.
Throughout the day, your eyes continuously produce mucus and oils to stay lubricated and protect themselves from dust, dirt, and microbes. Normally, when you’re awake, blinking helps spread these fluids evenly and clears away any buildup. But during sleep, because your eyes stay closed and blinking stops, all those materials accumulate at the inner corners of your eyes. By morning, they form the familiar crusty or gooey substance you wipe away without much thought.
The slightly yellowish tint of the discharge is actually due to the presence of dead bacteria that your immune system has been fighting off while you slept. In a vivid metaphor, Huberman describes these dead bacteria as “casualties of a war” your body wages overnight to keep your eyes clean and healthy.
While a small amount of eye discharge upon waking is completely normal and even a good sign that your eyes are doing their job of self-protection, there are some situations where it could indicate a problem. If you notice that the discharge is especially heavy, thick, or sticky—or if it’s accompanied by redness, itching, swelling, burning sensations, or blurry vision—it could point to an underlying condition, such as an eye infection. Conjunctivitis, often referred to as pink eye, is a common culprit that can cause these symptoms and may require medical treatment.
Other potential causes of excessive or unusual eye discharge include allergic reactions, blocked tear ducts, or more serious bacterial or viral infections. In those cases, it’s best to consult an eye care professional to get an accurate diagnosis and appropriate treatment.
Overall, though, that bit of crust in your eyes each morning is usually nothing to worry about. Instead, it’s a reminder of the incredible, behind-the-scenes work your body does while you sleep—keeping your eyes clean, hydrated, and ready to take on a new day.