system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do our eyes produce yellow crusty stuff?
gpt
That crusty stuff is a byproduct of the natural moisture of our eyes. Everyone we blink we refresh that moisture and in the process we flush some existing liquid and any dust from the air that’s gotten into our eyes away. The yellow crust is the result of that flushed liquid/dust accumulating and drying.