A sneeze is the semi-autonomous, convulsive expulsion of air from the nose. A sneezer exhales with a speed of up to 146 m/s (312 miles per hour). An unimpeded sneeze sends two to five thousand bacteria-filled droplets into the air.
Sneezing 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.
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.
Among the pagans of Flanders, a sneeze was an omen. When Saint Eligius (died 659/60) warned the pagans of Flanders against their druidical practices, according to his companion and biographer Ouen, he included the following: "Do not observe auguries or violent sneezing or pay attention to any little birds singing along the road. If you are distracted on the road or at any other work, make the sign of the cross and say your Sunday prayers with faith and devotion and nothing inimical can hurt you."
Roman Catholics Christianize this pagan custom with the following tale: The custom of saying "God bless you" after a violent 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. This custom persists among speakers of many languages: common social responses to sneezes in English include "Bless you" and "Gesundheit" (German, "health").
Sneezing in India provokes a shorter response. Bystanders to a sneeze shout, "Live!" eliciting a response from the sneezer, "Live with you!" Most Indians consider sneezing healthy: it is the inability to sneeze that is cause for alarm. Psychology Today reports Indian scientists have labeled an inability to sneeze "asneezia" and the people of India have long used snuff as a way to artificially induce the healthy sneeze.
Sneezing in Scandinavian countries like Sweden, Norway, and Denmark is usually replied to with "prosit"; "may it benefit" in Latin. The same word has also been used historically as a toast to a person's health while drinking. While it was never used in Scandinavian countries for this reason, the word "prosit" is still commonly used in Bavarian drinking songs.
In true muslim society, anybody who sneezes has to thank Allah by saying "Alhamdulillah". That is how a person thanks almighty Allah for keeping him alive and safe even after a 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. (also used for magpies)
- One for a wish
- Two for a kiss
- Three for a letter
- Four for something better.
Photic sneeze reflex