That yellow stuff in the corners of your eyes when you wake up—often called “sleep” or eye discharge—is perfectly normal. It’s a mix of mucus, oils, dead skin cells, and even some bacteria. While you’re asleep and not blinking, these materials naturally collect in the corners of your eyes. It’s just part of your body’s way of maintaining healthy, moist eyes overnight.

The yellow color mostly comes from dead bacteria that your immune system has fought off during the night. Your eyes are constantly exposed to irritants, so this discharge is a sign that your body is defending itself. It’s like a quiet overnight clean-up crew working while you rest. Pretty amazing, right?