You’ve probably noticed it countless times — that little bit of yellow or crusty residue that collects in the corners of your eyes when you wake up. Some call it sleep, eye gunk, or crusties, but few people really know what it actually is or what causes it.
While it’s a completely normal occurrence in most cases, the color, texture, and amount of discharge can sometimes reveal important clues about your eye health. Here’s what science — and eye doctors — say about that yellow stuff in your eyes every morning.
What Is the Yellow Stuff in Your Eyes?
The yellowish or whitish material that appears in your eyes after sleeping is called rheum. It’s made up of a mixture of mucus, oil, skin cells, tears, and other debris that accumulate while your eyes are closed.During the day, blinking helps wash away these secretions with fresh tears. But while you’re asleep, you don’t blink, allowing these substances to dry and build up in the corners of your eyes or along your lashes.
Why Does It Happen More at Night?
Your eyes are constantly producing a thin film of tears to stay clean and lubricated. At night, your tear production slows down, and blinking stops entirely. This means your body has fewer ways to flush out normal secretions and microscopic debris.
As a result, mucus and oil from your tear glands combine with small particles — like dust or dead cells — to form that familiar crusty buildup by morning.When It’s Normal vs. When It’s Not
A small amount of clear, white, or slightly yellow discharge in the morning is perfectly normal. However, changes in color, consistency, or quantity can signal that something isn’t right.
If the discharge becomes thicker, greener, or sticky, or if it’s accompanied by redness, pain, or blurry vision, it could be a sign of an eye infection or allergy that needs medical attention.
Possible Causes of Excess or Yellow Eye Discharge1. Conjunctivitis (Pink Eye)
One of the most common causes of excessive or yellow discharge is conjunctivitis, often called pink eye. This infection — caused by bacteria, viruses, or allergens — leads to inflamed eye membranes.If your eyes are stuck shut in the morning or you notice yellow-green pus-like discharge, it may be a bacterial infection requiring antibiotic eye drops.2. Allergies
