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MLA Full: "What Are Eye Boogers?" YouTube, uploaded by SciShow, 26 March 2016,
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Eye boogers: Not the most glamorous of bodily secretions, but important all the same. Learn why the heck you have sand in your eyes in the morning in this episode of Quick Questions.

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So, Mr. Sandman, I asked you to bring me a dream, and you brought me these gross eye boogers. Ok, but, what actually is this goopy junk that gathers in the corners of my eyes while I'm asleep? You might know it as eye boogers, sleepies, dream dust, sleep sand, or the sleep in your eyes. Scientist actually don't have a standard technical term for this crusty eye residue, but some call it gound or rheum. Which is much less fun to say. 

Rheum is a term for any thin discharge that comes from mucus-y parts of your body, like your eyes and nose. The kind that comes from your eyes is made up of all kinds of junk, like mucus, dead skin cells, oil, dust and bacteria. This delightful mixture gathers and dries to form a crusty residue in the corners of your eyes after you've been snoozing for a while. 

But then, why do eye boogers only seem to build up when we're sleeping? Well, it turns out that gound, or at least the things in it, is kind of always there. You just don't know that it's there most of the time.

Your eyeballs need to be kept nice and wet to function, so they're protected under this watery coating called tear film. a tear film actually has a couple of parts: an inner layer of watery mucus that coats your cornea and keeps you eye lubricated and a thin oily layer on top to keep all of the moisture inside. 

So normally when you're awake, any crud that gets in your eye is washed away by this tear film whenever you blink. Your eyelids are a lot less active when you're asleep, though. When you close your eyes for the night, or even just for a nap, you stop blinking, which means you're not clearing out all that debris. So it builds up, along with some of the mucus and oil from your tear film and collects in the corner of your eye. Before you know it, you have eye boogers in all of their crusty, cruddy glory. 

Some gound is dry and crumbly, and some is wet and sticky, it all depends on what's in your tear film. For example, people who have allergies tend to rub their eyes or produce more eye mucus, so there's more gunk floating around, which mean goopier eye boogers. Gross, yes. Dangerous? Not usually.

But excessive eye boogers can be a sign of more serious health problem. People with certain eye conditions, such as overactive oil glands or blocked tear ducts, can have more eye discharge and residue buildup. And with some infections, like pinkeye, the gunky buildup can get so bad that people can't open their eyes in the morning. Those are some strong boogers. But don't worry, for the vast majority of people, gound is normal and harmless.

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