That crusty buildup in the corners of your eyes when you wake up—often called 'sleep,' 'rheum,' 'eye boogers,' or 'sleepy dust'—is completely normal. But what's really going on?
It forms in the plica semilunaris, the small fold of mucous membrane at the inner corner of your eye where the tear ducts drain. Overnight, your eyes produce mucus and collect debris like tiny dust particles, pollen, and dead skin cells that didn't flush out during the day. This mucus is thicker than tears, so it accumulates and dries into that familiar crust. If your eyes stay well-lubricated with tears, the discharge remains moist and sticky; with dry eyes, it turns flaky and grainy.
