Q: Eye boogers. There, I said it. What in the world are they?

A: I’ve often wondered the same thing myself since I happen to be a prolific producer of the mysterious dried gunk otherwise known as “crusties,” “crud,” “eye goop,” “eye sand,” “fairy dust,” “sleep dust,” or what my mother liked to refer to as “sleepies.” In fact, one of the most crucial parts of my morning ritual next to caffeine guzzling and tongue scraping involves clearing away those crusty deposits around my eyes. Inevitably, many times I’ll miss a spot or a well-concealed nugget will emerge later on in the day, leading to some kind, observant and most likely grossed-out soul pointing out the obvious: I have something resembling a booger in one of my eyes.

The scientific name for eye boogers is rheum and the substance itself, a watered down cousin of phlegm, is different from your typical nose booger that’s composed of dried nasal mucus. Dried rheum found in the eyes, or gound, is made up of a delightful mixture of mucus discharged by the eyes, and dirt, dust and dead skin cells from the eyelids.

Your eyes — specifically a tiny, moon-shaped part of the eye called the plica semilunaris — produce rheum in its more viscous state 24/7 but thanks to blinking, you wash it away without ever really noticing. When you’re sleeping (and not blinking), however, small amounts of rheum can accumulate and dry up and harden in the corners of your eyes. This is the reason behind that booger-y surprise, delivered courtesy Mr. Sandman, each morning.

People produce varying amounts of rheum, and if you happen to generate what you think is an above average amount, it doesn’t necessarily mean that something is medically wrong with you. I suppose you could just think of your rheum-producing prowess as a special talent that involves bodily functions, like gleeking or the ability to belch vigorously. However, if it ever gets to the point that you can’t open your eyes in the morning because they’ve been sealed shut with think layers of dried gunk, then something is probably up — allergic conjunctivitis could be one culprit — and you should consult a doctor.

And as far as I know, there isn’t any “proper” way to remove dried rheum other than washing it off in the shower or gently wiping it away (with clean hands) and flinging it at an unsuspecting victim like the annoying, loudmouthed woman waiting in line in front of you during your morning Starbucks run (only semi-kidding). Sometimes, in the event of heavy, particularly sticky build-ups, you may want to use a Q-tip or a cotton ball.

Finally, if you’re not sufficiently grossed out enough already, you’re probably also wondering if there are any folks out there who eat eye boogers as a method of disposal. Although I’ve never witnessed anyone do this, I’m guessing some folks (and this dog) are in the (bad) habit of harvesting and then ingesting dried rheum. And from what I gather, eye booger eating, like regular booger eating, or mucophagy, won’t kill you, although it’s never a great idea to stick potentially germy fingers in your mouth.

So there you have it … the glorious world of gound and ocular mucophagy. Hope I didn’t ruin your appetite.

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.