Ever wake up with that sticky, yellowish gunk in the corners of your eyes? Commonly called "sleep," this crusty residue (officially known as *rheum*) is a natural part of your eye’s self-cleaning process. But what exactly is it—and why does it appear overnight?
### **What’s in Eye Discharge?**
According to neuroscientist Andrew Huberman, this morning buildup is a mix of:
- **Mucus** (to trap debris)
- **Oils** (from your tear film)
- **Dead skin cells** (shed from your eyelids)
- **Dead bacteria** (yes, really!)
That last ingredient might sound alarming, but it’s actually a sign your immune system is hard at work. The yellowish tint? That’s from white blood cells that fought off bacteria while you slept—leaving behind microscopic "battle debris."
### **Why Does It Form Overnight?**
During the day, blinking constantly flushes away debris and keeps your eyes lubricated. But when you’re asleep:
✔ **Your eyes stay closed**, reducing tear circulation.
✔ **Debris accumulates** in the inner corners.
✔ **Your immune system** keeps working, fighting bacteria and irritants.
Huberman compares it to a nightly "clean-up crew" sweeping away the day’s invaders. By morning, the leftovers clump together, forming that familiar crust.
### **When Is It Normal—And When Should You Worry?**
Small amounts of eye gunk are healthy—it means your eyes are self-cleaning. But see a doctor if you notice:
🔴 **Excessive discharge** (especially green/gray)
🔴 **Redness, swelling, or pain**
🔴 **Blurred vision or light sensitivity**
These could signal an infection like *conjunctivitis* (pink eye) or a blocked tear duct.
### **A Fresh Perspective on Eye Gunk**
Instead of seeing it as gross, think of morning eye crust as proof your body’s defenses never take a break. While you’re peacefully asleep, your immune system is on patrol—keeping your eyes healthy so you can wake up clear-eyed and ready for the day.
So next time you wipe away that little yellow glob, remember: it’s not just gunk. **It’s biology in action.**
