When you wake up and notice yellow goop in the corners of your eyes, you’re seeing what’s commonly referred to as “sleep” or eye discharge. While it might look unpleasant, it’s actually a normal byproduct of your body’s nightly self-cleaning process.

This discharge is made up of a mix of mucus, oils, dead skin cells, and according to neuroscientist Andrew Huberman, even dead bacteria. These elements combine during the night as your body works to maintain eye health while you rest.

During the day, blinking helps your eyes clear out debris. But when you sleep, you don’t blink, allowing this mixture to accumulate in the corners of your eyes. By morning, the yellowish crust has formed as a result of your eye’s natural defense system at work.

The yellow tint specifically comes from dead bacteria your immune system has fought off overnight. In a vivid analogy, Huberman likens the crust to the “casualties of a war”—a sign that your body has been protecting your eyes while you were unaware.

Under normal conditions, this discharge is harmless and even a sign of healthy immune function. It’s your body clearing out unwanted material and maintaining a clean surface for your eyes.

However, if you notice the discharge is excessive, sticky, or accompanied by redness, swelling, itching, or burning, it could signal an eye infection such as conjunctivitis (pink eye). In such cases, it’s important to see a doctor for diagnosis and treatment.

Infections aside, regular morning eye discharge is just one of the many ways your body maintains health during rest. It’s a small reminder that while you sleep, your immune system remains active, quietly doing its job.

So next time you wipe your eyes in the morning, think of it not as a nuisance, but as a sign your body is working hard to keep your eyes safe and clean—even while you dream.