<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (April 2018) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (April 2018) (Learn how and when to remove this template message) </Td> </Tr> <P> Rheum (/ ˈruːm /; from Greek: ῥεῦμα rheuma "a flowing, rheum"), also known as gound, is thin mucus naturally discharged from the eyes, nose, or mouth during sleep (cf . mucopurulent discharge). Rheum dries and gathers as a crust in the corners of the eyes or the mouth, on the eyelids, or under the nose . It is formed by a combination of mucus (in the case of the eyes, consisting of mucin discharged from the cornea or the conjunctiva), nasal mucus, blood cells, skin cells, or dust . Rheum from the eyes is particularly common . Dried rheum is commonly called sleep, sleepy - seeds, sleepy buds, sleepy sand, eye goop, cheese, or sleepy dust . </P> <P> When the individual is awake, blinking of the eyelid causes rheum to be washed away with tears via the nasolacrimal duct . The absence of this action during sleep, however, results in a small amount of dry rheum accumulating in corners of the eye, most notably in children . </P>

Where does the crust in your eyes come from