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Nose-picking is the act of extracting mucus or foreign bodies from the nose with a finger. Compulsive nose-picking is known as rhinotillexomania (etymology: Greek, rhino "nose" + tillexis "habit of picking" + mania).
Although a very common habit, it is a mildly taboo subject in most cultures. Children's literature often makes reference to it, to amuse readers (for example Jacques Charpentreau's poem "De l'Education!" and Gordon Korman's Nose Pickers series). John Allen Paulos's imaginary novel, Rucker: a life fractal has a section where "proboscis probing is discussed at length." 
Mucophagy is the consumption of the mucus thus extracted, and is commonly referred to as "picking your nose and eating it" (where 'it' refers to the mucus rather than the nose). While common in some cultures, it is also generally viewed as a cultural taboo, to the extent that many of those who engage in the practice generally find it disgusting when done by someone else in their presence, much like flatulence or masturbation.
Nose-picking may carry a number of medical risks, including causing nasal infections and nosebleeds. Most authorities recommend using a tissue.
However, at least one well-known doctor sees nose-picking and mucophagy as beneficial.  He states that not only is the finger capable of reaching parts of the nose that a handkerchief or tissue is unable to, thus keeping the nose cleaner, but that eating the bacteria-rich dried mucus offers a boost to the immune system, and is analogous to immunization.
Due to the special nature of the blood supply to the nose and surrounding area, it is possible for retrograde infections from the nasal area to spread to the brain, although this scenario is unlikely to arise from nose-picking. For this reason, the area from the corners of the mouth to the bridge of the nose, including the nose and maxilla, is known to doctors as the "danger triangle of the face."
"You can pick your friends and you can pick your nose, but you can't pick your friend's nose." is a well known joke in English-speaking culture.Popular sayings and jokes reveal social attitudes about nose-picking, similar to toilet humor.
"You can pick your friends, but you can't pick your nose."
"You can pick your friends and you can pick your nose, but you can't pick your friend's nose."
"You can pick your friends, and you can pick your nose, but you can't wipe your friends under the sofa."
"What is the difference between boogers and broccoli? Kids won't eat broccoli."
"How did you know I went to Harvard? I noticed your class ring when you picked your nose."
"I know he picks his nose. I felt under his furniture."—Van Lane Ferguson, We Bark at Midnight (1962)
"If I had a million boogers, I'd still pick you."
"Pick 'em, lick 'em, roll' em, flick 'em."
"Booger, booger, in my nose. Pick it, flick it; there it goes."
"I guarantee you that Moses was a picker. You wander through the desert for forty years with that dry air. You telling me you're not going to have occasion to clean house a little bit."—Seinfeld episode "The Pick" (1992)
"What is the most musical part of your body? Your nose, because you can pick it...AND BLOW IT!!!"— Fresh Prince of Bel Air when Will gets hypnotized and becomes a 5-year old.
"How come I can pick my friends but not my nose? Who made up that rule anyway? How can you say 'that's the way it is, that's just the way it goes'? Why don't you decide for yourself what you can do and what you can say."—Ani DiFranco
"The doctor said I wouldn't have so many nosebleeds if I kept my finger out of there."—Ralph Wiggum, The Simpsons episode "I Love Lisa"
"Remember Ralphie, if your nose starts to bleed it either means you've been picking your nose too much—or not enough."—Chief Wiggum, The Simpsons
"Hey, Mom, what's for dinner? Go up your nose and pick a winner!"—Biz Markie, the song "Pickin' Boogers"
"Everybody knows, (Insert Name) picks his/her nose, rubs it in the dirt and eats it for dessert" is a common children's rhyme in Australia and New Zealand, used in playground taunting.
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