Cue "Mr.  Sandman" and read on....

Are you a crumbly eye booger person, or a mucous eye booger person?  If you're like most Americans, you've questioned why we get eye boogers, especially while sleeping.  This should clearly (like Visine) spell it out for you.

Some of the evidence of a night's sleep are visible when you lift your head off the pillow -- bed head, morning breath, dried-up drool, and eye boogers.

And while the cause of most of these sleep remnants is fairly obvious, the reason behind those sometimes-sticky, sometimes-crusty gobs of crud that can dot the lashes or cling to the corners of the eye is less clear. Why do our peepers churn out this gunk at night and what's in the stuff? For answers to these important questions, Body Odd turned to an eye expert.

"The general consensus is that this debris is the stuff leftover from dried out tears," says Dr. Sherleen Chen, director of the cataract and comprehensive ophthalmology service at Massachusetts Eye and Ear Infirmary in Boston.

Tears are made up of water, protein, oils, and a mucous layer known as mucin, which typically coat the surface of the eye to moisten and protect it from viruses and bacteria.  But when your eyes are closed and your eyelids are not blinking, dirt and debris within the eye isn't continually washed over by tears, which would help to dilute them. So at night, dryness causes the stuff in tears to precipitate out, explains Chen. Then the crud collects toward the inside corner of the eye, where tears usually end up.

Eye boogers can also accumulate on the outer corners of the eye or anywhere along the lash.

There's also the question of its consistency -- sometimes "eye boogers" are wet and sticky and other times they're dry and sandy. Does this depend on how long they've sat there or how much sleep you've gotten?

Chen says the texture is a function of a person's tear film. The crud is crumbly in people whose eyes tend to be dry -- their peepers have more solids and not enough liquid.

Folks who have more allergies, tend to have more mucous, which gives eye crud a wetter, gunkier quality to it.

People who wear contacts are prone to forming more "sleepy sand" because the lenses irritate the surface of the eye, so it produces more mucous to protect itself.

Although not an attractive look first thing in the morning, the stuff is basically harmless.

Chen says the best way to clear eye boogers is to lay a hot washcloth on the lid and lashes for a minute or two, then gently clean them off.

Information via:  Cari Nierenberg/The Body Odd-on MSNBC.COM