HEALTHY LIVING
05/29/2014 08:20 am ET | Updated Feb 05, 2015

Why Do We Get 'Sleep' In Our Eyes?

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Why do we get "sleep" in our eyes?

You may call it "sleep," others might call it "crust" or "sand." Some doctors call it "mattering," and a less-commonly used term is "rheum." But no matter the name you use, you know it when you see it -- that white-yellow crumbly gunk on your eyes after you've had some shut-eye.

The crusty stuff is actually made up of a bunch of different materials, including discarded cells, mucus and debris (including bacteria, bits of oil from the eyelids, and dust), that are collected as the eyelids sweep across the eye, explains Dr. Ivan Schwab, M.D., a professor of opthalmology at the University of California Davis School of Medicine and a member of the American Academy of Ophthalmology.

Our eyelids close similarly to a zipper, from the cheek side toward the nose. When they do that, they push the tears across the eye, picking up all these different materials along the way. This discharge ultimately collects in the corner of the eyes or the lower lid, and a bit may also collect on the upper lid, he says.

"It may be a bit like using an exfoliant on your skin: You're cleaning off dead skin or any surface debris you don't want," Schwab explains to HuffPost.

So is "sleep" clean? Schwab says that it's not sterile -- nothing on your body really is, including the surface of your eye, or even the surface of your skin. That being said, if you use your hands to wipe away eye crust (which you shouldn't be doing in the first place, Schwab says -- a warm, wet washcloth is better for cleaning your eyes) -- it is probably a good idea to wash your hands afterward.

Normal "sleep" has a slight cream-like tint to it, though it could appear darker if you wear makeup. An active bacterial or viral infection could also increase the amount of eye discharge, and make it more yellow- or green-tinted (at which point, you should see an eye doctor).

Eye discharge that's on the drier side may be indicative of a drier environment, Schwab says. In addition, you might experience more eye discharge if you have an increase in mucus -- allergies are a big culprit.

"The eye produces mucus in response to allergens in the air," according to Schwab. "Allergies like pollen, they get in the eye [and] they cause the eye to create mucus [that] surrounds the pollen and takes it to the corner" of the eye.

In addition, contact lens-wearers may experience more eye discharge because they are technically walking around with a foreign body in their eyes all day. If a contact lens fits perfectly, you'll still experience a little excess mucus production -- and if the contact lens fits less than perfectly, or traps debris (such as pollen) beneath the lens, then the eye will produce even more mucus, he says.

Changes to the amount of eye "sleep" your body is producing could be a sign of an eye infection or other problem. Meanwhile, if you have chronic discharge that hasn't changed (but there's a lot of it), that could reflect something else, such as irritation from dust, or even allergies. If you have so much eye crust along your lashes to the point where your eyes are stuck together in the morning, this could actually be a sign of blepharitis, a disorder where there is a low-grade inflammation of the eyelids.

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