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The Science Behind Sneezing

A woman wearing an olive green shirt and a muted pink blazer sits at a table with a coffee cup and laptop open, leaning her face into her right elbow to sneeze

What Happens When You Sneeze? 

Sneezing has taken on an entirely new look in the age of COVID-19. 

The sneezer scrambles to sneeze into their sleeve and then apologizes. The folks around the sneezer appear to panic and almost run for cover fearing that infected droplets may be flying at them. 

So, since we’re still in cold and flu season as well as struggling with seasonal allergies as clouds of pollen surround us, it’s the perfect time to talk about what happens when you sneeze. 

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 seventh century, who would bless those who sneezed so they wouldn’t fall ill to the plague. 

Another explanation points to the Greek word for sneeze, “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,” located in the lower brain stem, is triggered. It 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. Suddenly, air, saliva and mucus are forced out of your nose and mouth. 

AAAAAHHHH-CHOOOO. Voilà, a sneeze! 

It’s a little gross, but it’s 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. Yep, that’s why covering your nose and mouth when you sneeze is a good thing, even without COVID-19 fears.
  3. Those droplets can linger in the air for 10 minutes.
  4. A sneeze is a nasal restart: Whatever irritated your 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.


So much happening in such a short time. It’s another sign of just how amazing our bodies really are. Now go enjoy that sneeze but cover your nose and mouth when you do! 

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PBS North Carolina and Sci NC appreciate the support of the NC Department of Natural and Cultural Resources.
PBS North Carolina and Sci NC appreciate the support of The NC Department of Natural and Cultural Resources.