It's probably not something you think about too often, but there are some fascinating facts about the old ah-choo. Also called sternutation, sneezing is the body's way of clearing the nose of bacteria, viruses and irritants such as dust or perfume.

When nerve endings in the lining of the nasal passages are stimulated, the "sneeze center" in the lower brain stem sends out signals that cause you to take a deep breath and hold it. Air pressure in the lungs increases...chest muscles tighten.. and your throat and eyes close. Then your chest muscles contract vigorously and your throat muscles relax, abruptly forcing air from your nose and mouth at about 100 miles per hour and sending out a wet spray that can radiate five feet.

Curious triggers: Sneezing doesn't occur only when you have a cold or allergies. The sneezing reflex can be provoked by all kinds of odd things, from sunlight to exercise to sex, according to allergist Neeta Ogden, MD, a spokesperson for the American College of Allergy, Asthma and Immunology. Here are some surprising sneeze triggers.. and what you can do to halt inopportune sneezes before they erupt.

  • Eyebrow plucking. This stimulates the trigeminal nerve that supplies sensation to the face, firing impulses that reach the nerve endings inside the nose and sparking the sneezing reflex

Preempt the sneeze: "Press a fingertip on your eyebrow while tweezing to interrupt this nerve messaging and dampen the impulse to sneeze," Dr. Ogden suggested.

  • Exercising. Working out causes you to hyperventilate, which can dry out your nasal passages. In response, your nose increases its mucous secretion and that can stimulate the nerve endings that provoke sneezing. Heavy breathing also stimulates the diaphragm, contributing to the sneezing reflex.

Preempt the sneeze: Hydrate your nose with a few spritzes of saline mist just before a vigorous workout, Dr. Ogden advised. If sneezing is truly disruptive, try a lower-intensity exercise such as walking, yoga or Pilates

  • Bright light. Do you sneeze after walking out of a dark theater and into the bright afternoon sunlight? Called the photic sneeze reflex, this inherited trait affects an estimated one-third of people.

Spice Allergy Affects 2% to 3% Of the Population

It is more common in women than men and often is triggered by cinnamon, garlic, vanilla, black pepper or spice blends. Reactions, which can range from mild sneezing to life-threatening anaphylaxis, can be caused by breathing, eating or touching spices. Spices also are found not just in food but in a variety of cosmetics and dental products.

Possible explanation: When the optic nerve is stimulated by a sudden flood of bright light, it fires a signal to the brain to constrict the pupils—but some of that electrical signal is picked up by the nearby trigeminal nerve and mistaken as a nasal irritant.

Preempt the sneeze: Put on a pair of sunglasses before going out into bright light...or try breathing through your mouth while pinching the end of your nose for a few moments to disrupt the errant nerve signal.

  • Sex. Physical intimacy activates the parasympathetic nervous system that controls involuntary reflexes-reflexes that include sexual arousal and sneezing. This link may be behind the "nuisance sneezing that occurs during sex, Dr. Ogden said. Also, the nose (like the genitals) contains erectile tissue that may become engorged during arousal, provoking a sneeze.

Preempt the sneeze: Try using the length of your index finger to press gently but firmly on the area between your nose and your upper lip until the sneezing urge passes then you can carry on with what you were doing, free of distractions.

Last word: The brain's sneeze center and related nervous system circuitry relax during sleep, Dr. Ogden noted, which is why we generally don't sneeze while as you drift off, rest assured that sneezes won't disturb your post-afterglow slumber.

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