Dr. Universe,

Why do we sneeze?

— Nyuma, 10, North Carolina

Dear Nyuma,

Imagine you are home sick from school or are just playing outside when all of a sudden ... ah-ah-ah-choo. It might seem like that sneeze came out of nowhere, but a lot of things went on in the brain and body to make it happen.

That’s what I found out from my friend Hans Haverkamp, a scientist at Washington State University who is really curious about the human body and how it works.

Your body’s muscles tense up and contract, making a sneeze “seriously explosive,” said Haverkamp. “Bam. Air comes flying out of your mouth, along with a bunch of germs.”

A sneeze, or a sternutation (stir-new-TAY-shun), is a kind of reflex that helps protect you from things like dust, pollen or chemicals in irritating odors. There are lots of different kinds of reflexes. If you’ve ever had a doctor tap your knee with a tiny rubber hammer, you may have felt the knee-jerk reflex before. A hiccup is another kind of reflex.

These are involuntary responses — you don’t even have to really think about it. The brain and body automatically take care of it for you.

In your body there are billions of nerve cells that help you feel and sense the world. They help with smell, sight, touch, taste and hearing. When nerve cells in your nose sense that there is something in the nasal passageway that isn’t supposed to be there, they help send a signal to your brain. When the signal reaches your brain, it creates an automatic response and you start getting sneezy.

It takes muscles like your abdomen and your larynx, or voice box, to help push out a sneeze, too. The mucus that lines your nose and airways also helps grab onto some of those small invading particles. Sometimes a sneeze comes with a lot of snot, or mucous, too. It’s important to cover your sneeze to keep germs from flying out and landing on other people.

All kinds of animals sneeze, including cats, dogs and mice. Elephants sneeze out of their trunks, which is their nose. There are also animals like Galapagos marine iguanas that sneeze to get rid of sea salts that come from the process of digesting their food.

When humans sneeze, we will often hear other people say “bless you” or “gesundheit.” The phrase “gesundheit” is German and means “health.” “Bless you” comes from the sixth century when people had the plague and used this phrase in hopes people would get better soon.

According to the Guinness World Records, the longest sneezing fit, or most sneezes in a row, went to a woman in the United Kingdom. She sneezed about a million times in the first year and had her first day without a sneeze after 977 days. That must have been a lot of tissues.

But usually a sneeze is a sign that you have a cold or allergy and that your body is working hard to help you stay healthy.

— Dr. Universe


Have a science question? Ask Dr. Wendy Sue Universe, WSU’s resident science cat and writer, by email at Dr.Universe@wsu.edu, on her website at askDrUniverse.wsu.edu, via Twitter at @AskDrUniverse or at facebook.com/AskDrUniverse.

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