why do we sneeze | smarteducational learners | Surprising Sneezing Facts | sneezing superstitions

A sneeze, or sternutation, is a semi-autonomous, convulsive expulsion of air from the lungs through the nose and mouth, usually caused by foreign particles irritating the nasal mucosa. ... The function ofsneezing is to expel mucus containing foreign particles or irritants and cleanse the nasal cavity.

         Sneeze: to make a sudden violent spasmodic audible expiration of breath through the nose and mouth, especially as a reflex act.

The nose provides the main route through which inhaled air enters and leaves the lower airways. Because of its position, it serves numerous functions. The narrowing passageways cause inspired air to flow with increased turbulence. This turbulence, in turn, increases the interaction between the airstream and the nasal mucosa (lining of the nose), allowing for heat and moisture to be exchanged, and for suspended or soluble particles from the air to be cleared.

Sneezing is a physiologic response to the irritation of the respiratory epithelium lining of the nose. The process usually begins with the release of chemicals such as histamine or leukotrienes. These substances are manufactured by inflammatory cells such as eosinophils and mast cells typically found within the nasal mucosa. The chemical release is caused by viral respiratory infections, filtered particles, allergens (substances that trigger allergic reactions) or physical irritants such as smoke, pollution, perfumes and cold air. Allergic reactions with the nasal mucosa require the presence of IgE (allergy antibody specific for the allergen). This leads to fluid leakage from vessels in the nose, causing symptoms of congestion and nasal drip. Additionally, nerve endings are stimulated, leading to the sensation of itching.

Ultimately, the nerve ending stimulation leads to activation of a reflex inside the brain. The nervous impulse travels up the sensory nerves and down the nerves controlling muscles in the head and neck, and that leads to the rapid expulsion of air. The high velocity of the airflow is achieved by the buildup of pressure inside the chest with the vocal cords closed. The sudden opening of the cords allows the pressurized air to flow back up the respiratory tract to expel the irritants. This helps to remove offending particles in the nose. However, in infected individuals, it also allows for the spread of the common cold, as innumerable viral particles are contained within each droplet of mucus expelled.

Various medications are available to help control this reaction. Antihistamines act principally by blocking the action of histamine at receptors located on the blood vessels in the nose. Some prescription antihistamines are nonsedating, compared with their over-the-counter counterparts. Decongestants stimulate receptors located on the same vessels to cause constriction and lessen the congestion. Topical nasal steroids are used in allergic patients to reduce the number of inflammatory cells and ultimately inhibit the release of histamine.

11 Surprising Sneezing Facts

1. "Sneezes start in your nerves," says Neil Kao, MD, an allergy and asthma specialist at the Allergic Disease and Asthma Center in Greenville, S.C.

Everyone's nervous system is basically wired in the same way, Kao explains. But signals traveling along nerves can take slightly different paths to and from the brain, resulting in different sneeze scenarios from person to person.

"It's a nerve transmission that tells your brain something is in your nose that needs to come out," Kao tells WebMD.

2. Sneezing helps keep your body safe. "Sneezing is an important part of the immune process, helping to keep us healthy and sniffle-free," Kao says.

Sneezes protect your body by clearing the nose of bacteria and viruses, Kao explains. When something enters your nose or you encounter a trigger that sets off your "sneeze center" in your brain, located in the lower brainstem, signals are rapidly sent to tightly close your throat, eyes, and mouth. Next, your chest muscles vigorously contract, and then your throat muscles quickly relax. As a result, air -- along with saliva and mucus -- is forced out of your mouth and nose. Voila, you've sneezed.

3. Sneezes are speedy. "Sneezes travel at about 100 miles per hour," says Patti Wood, author of Success Signals: Understanding Body Language. She adds that a single sneeze can send 100,000 germs into the air.

4. Plucking your eyebrows may make you sneeze. Plucking may set off a nerve in your face that supplies your nasal passages. As a result, you sneeze.

5. You don't sneeze in your sleep. When you sleep, so do your sneezing nerves -- which means you usually don't sneeze when you doze.

6. Your workout may make you sneeze. "Exercise can make you sneeze," Kao says. "You hyperventilate when you're over-exerted, and as a result, your nose and mouth start to dry up. So your nose reacts by starting to drip, making you sneeze."

7. The longest sneezing spree: 978 days, a record set by Donna Griffiths of Worcestershire, England, according to background information on the Library of Congress' web site.

8. Sunshine may make you sneeze. "Bright sunlight causes one out of three people to sneeze," Wood says. "The light sneezers are called 'phonics,' from the Greek meaning ‘of light.' And in fact, light sensitivity is an inherited trait -- just one more thing we can blame on our parents."

9. Sex can be a sneezing trigger. Have sex, must sneeze? It happens more often than you might think. Researchers believe that the stimulation of the parasympathetic nervous system fires off signals in some people to not only enjoy the act of sex but to sneeze when it's over.

10. The sneeziest animal: the iguana. Iguanas sneeze more often and more productively than any other animal, according to Wood's research. Sneezing is how they rid their bodies of certain salts that are the normal byproduct of their digestive process, Woods says.

11. How do you stop a sneeze? While it's not foolproof, "Try breathing through your mouth and pinching the end of your nose," Kao says.

Sneezing Superstition

Strange sneezing facts aside, there are some beliefs about sneezing that just aren't true.

For instance, it's not true that your heart stops when you sneeze. When your chest contracts because of a sneeze, your blood flow is momentarily constricted as well. As a result, the rhythm of your heart may change, but it definitely doesn't stop.

And your eyeballs cannot pop out of your head when you sneeze. Most people naturally close their eyes when they sneeze, but if they are able to keep them open, their eyes stay firmly planted in their heads where they belong. "While a person's blood pressure behind the eyes may increase slightly when he sneezes, it's not enough force to dislodge the eyeballs from the head," Kao says.

Wood has heard of other sneezing folklore, including the notion that if you sneeze, the company is coming over, and if your cat sneezes, it's going to rain.

As for the blessing many people say after someone sneezes, Wood explains that the Greek word for a sneeze is "pneuma," which means "soul or spirit."

"A post-sneeze blessing stems from the ancient belief that sneezing is a near-death experience and that a blessing will prevent your soul or sneeze from escaping your body and will deter the devil from entering in," Wood says.