What happens when you sneeze?

Do you know what happens when you sneeze and why?


What happens when you sneeze?
March 3, 2018

The origin of "bless you"

Have you ever wondered why people often say, “bless you” when you sneeze?

There are a couple of explanations. One ties to Pope Gregory VI in the sixth century, who would bless those who sneezed so they wouldn’t fall ill to the plague.

There’s another explanation that says the Greek word for sneeze is “pneuma,” which means soul or spirit. The belief was that sneezing is a near-death experience and that a blessing will keep you alive. That also links to the belief that your heart stops when you sneeze.

Sneezing protects the body

You can relax—your heart keeps beating throughout your sneeze.

And whether that sneeze takes the form of a loud bellow or roar, or even a tiny squeak, a sneeze is an important protection mechanism for the body.

Lydia Bourouiba, a mathematical physicist at MIT, helps to understand how a sneeze works. Her study of sneezing was published in the New England Journal of Medicine in 2016.

First, a sneeze starts in your nerves. When the lining of your nose gets irritated; from a cold, pollen, dust, smoke, pepper, etc., your body goes into reaction mode. Your “sneeze center” is triggered. It’s located in the lower brain stem. The sneeze center sends out a signal to tightly close your throat, eyes and mouth. Your chest muscles contract and compress your lungs while your throat muscles relax. All of that means air, saliva and mucus is forced out of your nose and mouth.

AAAAAHHHH-CHOOOO. Voila, a sneeze!

It’s a little gross, but also pretty amazing. Watch the slow motion sneeze video that accompanied the study here.

Nothing to sneeze at: the facts about sneezing

Here are a few other sneezy notes:

  1. Sneezes are fast — A sneeze travels at 100 mph and sends about 2,000-5,000 bacteria filled droplets into the air.
  2. Sneezes have distance — Those droplets can reach a five foot radius. (Now you can understand why your mom always said to cover your mouth and nose when you sneeze.)
  3. A sneeze is a nose restart — Whatever irritated the nose to create the sneeze overwhelmed the nasal system. So, much like shutting down a computer to restart the system, the sneeze resets the nasal environment. That’s why it’s common to sneeze several times in a row, if the irritant hasn’t cleared out.


—Frank Graff 

Frank Graff is a producer/reporter with UNC-TV, focusing on Sci Tech Now North Carolina, a weekly science series that airs Tuesdays on UNC-TV. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!