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Sneeze

A sneeze is generally caused by irritation in the passages of the nose. Pollens, house dust, and other particles are usually harmless, but when they irritate the nose the body responds by expelling them from the nasal passages. The nose mistakes strong odors, sudden chills, and even bright lights (see photic sneeze reflex) for parasites, and it tries to defend itself with a sneeze. A sneezer exhales with a speed of up to 46 m/s (104 miles per hour). An unimpeded sneeze sends two to five thousand bacteria-filled droplets into the air.

It is almost impossible for a person to keep their eyelids open during a sneeze. The reflex of shutting the eyes serves no obvious purpose: the nerves serving the eyes and the nose are closely related, and stimuli to the one often trigger some response in the other.

Orgasms amongst humans can also cause sneezes.

Superstitions about sneezing

In 400 BC the Athenian general Xenophon give a dramatic oration exhorting his fellow soldiers to follow him to liberty or to death against the Persians. He spoke for an hour until a soldier underscored his conclusion with a sneeze. Thinking this sneeze a favorable sign from the gods, the Greeks made Xenophon general and followed his command.

The custom of saying "God bless you" after a sneeze was begun literally as a blessing. Pope Gregory I the Great (540-604 AD) ascended to the Papacy just in time for the start of the plague in 590 AD (his successor succumbed to it). To combat the plague Gregory ordered litanies, processions and unceasing prayer for God's intercession. When someone sneezed, they were immediately blessed ("God bless you!") in the hope that they would not subsequently develop the plague.

Sneezing in India provokes a shorter response. Bystanders to a sneeze shout, "Live!" eliciting a response form the sneezer, "Live with you!" Most Indians consider sneezing healthy: it is the inability to sneeze that is cause for alarm. Science magazine reports Indian scientists have labeled an inability to sneeze "asneezia" and are currently researching ways to artificially induce the healthy sneeze.

Sneezing has also inspired superstition-laden nursery rhymes:

Sneeze on Monday for health, Sneeze on Tuesday for wealth, Sneeze on Wednesday for a letter, Sneeze on Thursday for something better, Sneeze on Friday for sorrow, Sneeze on Saturday, see your sweetheart tomorrow, Sneeze on Sunday, safety seek.

One for sorrow Two for joy Three for a letter Four for a boy. Five for silver Six for gold Seven for a secret, never to be told.