Also in this week's column:

• Why do some people have three nipples?
• Is it true that a woman's breasts can grow enormously overnight?
• Why do we open our mouths to yawn properly?

Why is it absolutely impossible to sneeze with your eyes open?

Asked by Jeff Grisham of San Antonio, Texas

One of the classic Odd Body Questions is why can’t I sneeze without closing my eyes. This question was answered in my first book, The Odd Body. The medical term for a sneeze is the “sternutatory reflex”. Almost all animals sneeze. A sneeze helps clear the nose and sinus regions while injecting oxygen into the cells of the body. A sniff does much the same thing. Nevertheless, a sneeze is a very complicated body action. Technically, a sneeze is produced when an irritant contacts the nasal mucosa, which in turn stimulates the trigeminal nerve, which in turn stimulates the pons and medullai of the brain, which in turn sets off additional nerve reactions, and so on. During a sneeze, tremendous stress is placed on the body. Considerable air pressure is place upon the eyes. This pressure is not enough to pop your eyes out of your head or even make them bulge out, but enough to make your eyes feel uncomfortable from the added pressure. According to Dr. G.H. Drumheller of the International Rhinologic Society in Milan, we close our eyes when we sneeze in order to keep the eyes from “extruding”.

Stephen Juan, Ph.D. is an anthropologist at the University of Sydney. Email your Odd Body questions to s.juan@edfac.usyd.edu.au

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• Does eating fish improve brain function? (10 November 2006)
• Why do I have an extreme fear of needles? (3 November 2006)
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