What 'Ah-Choo!' Can Do For You Sneezing spreads germs to innocent bystanders, but for the person doing the sneezing, it's the first line of defense against invaders. About 10 percent of the population sneezes when they're exposed to sunlight.
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What 'Ah-Choo!' Can Do For You

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What 'Ah-Choo!' Can Do For You

What 'Ah-Choo!' Can Do For You

What 'Ah-Choo!' Can Do For You

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We all know that sneezing spreads cold viruses. But it turns out that sneezes actually do some good — for the sneezer.

David Makiri sneezes into a tissue. Germs, dust and pollen that get inside the nose are no match for the mighty sneeze. Jonathan Makiri/NPR hide caption

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Jonathan Makiri/NPR

David Makiri sneezes into a tissue. Germs, dust and pollen that get inside the nose are no match for the mighty sneeze.

Jonathan Makiri/NPR

The sneeze is the body's first line of defense against alien invaders such as viruses and bacteria. Eli Meltzer, an allergist who is co-director of Allergy and Asthma Medical Group and Research Center in San Diego, says germs, dust, pollen and other irritants that make their way into the nose are no match for the mighty sneeze.

"It's powerful," Meltzer says. "We actually blow out the sneeze at 40 mph. The discharge can go 20 feet. And it's said that 40,000 droplets can come out when you spritz with the mouth and the nose when you sneeze."

And you don't have to be in great shape to rock a powerful sneeze. That's because we sneeze pretty much on autopilot. When the nerve cells inside of the nose detect an intruder, it starts an itch. That sends a signal to the brain.

"The signal to the brain causes a reflex," Meltzer says. "That reflex goes to the face and nose and chest. The person takes a deep breath because of that. Then they explode this air from their lungs through the mouth and nose."

Reasons For Sneezing

A montage of sneezes in slow motion.

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But for many people, sneezing doesn't end their misery. Once people have a cold, sneezing is just one more symptom. And for those with chronic allergies, sneezing can be a signal that they're feeling miserable. Those symptoms can last for weeks, months or years.

People also sneeze when they're not sick. Some people sneeze when they eat a really big meal. And about 10 percent of the population sneezes when they're exposed to sunlight. That's probably a genetic trait.

Louis Ptacek, a professor of neurology at the University of California in San Francisco, studies epilepsy and movement disorders. He's looked into the photic sneeze reflex for clues on how genes affect the brain and nervous system. "Photic sneeze is clearly not a disease," Ptacek says. The mechanism for photic sneezing is unknown, but it's probably some kind of glitch in the wiring among eyes, brain and nose.

Testing Sneezers

When we asked people at NPR headquarters in Washington, D.C., we found a lot of people who said they were photic sneezers. Bob Boilen is one of them. To test the reflex, we put him right by the window on a sunny day. But he didn't sneeze.

"I definitely feel inside all those tingly things that happen just before you sneeze," Boilen said. "Oh, what a letdown."

Other NPR employees said they always sneeze when they eat mints. But they, too, couldn't replicate those sneezes for us when we stood by with microphone and reporter's notebook.

Our experiment may have failed because of a basic rule of science: Observation affects the outcome of experiments. Ptacek told us one way we might have overcome that problem:

"I would be willing to bet a lot of money that if you took those people and you put them in a really dark room for two hours and then walked out into bright, bright sunlight, they'd have a much higher likelihood of sneezing," Ptacek says. "And it couldn't be suppressed by feeling self-conscious."

Want to stifle a sneeze? It's possible, Meltzer says. Just press hard on the bridge of your nose.