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Jessi: Hey! It's cleaning day! Today we're doing a little tidying up around the fort. We're sweeping and dusting... [sneezes] Oh, sorry guys. That was a big sneeze.

You know, when I think about it, cleaning's not the only time I sneeze. Sometimes I sneeze when I'm around flowers and I sneeze a lot when I have a cold. And I bet you can think of some things that make you sneeze too. It happens to everyone, but have you ever wondered why?

Every sneeze starts right inside your nose. The inside of your nose is covered with a lot of really tiny, really fine hairs and there's also a lot of mucus inside your nose. Yup, mucus, the same gooey, sticky stuff that shows up in your tissue when you blow your nose. The hair and mucus work together to catch tiny particles that are in the air that you breathe in, like bits of dust, pollen from flowers, or even the pepper you might put on your good.

These things clog up the inside of your nose causing it to get irritated, which means it gets kind of tickly. You might also feel that tickle when you're sick. That's because the inside of your nose is being attacked by lots and lots of tiny little things like viruses or bacteria. When your nose gets irritated by any of these things, it sends a signal to your brain that says "We gotta get this stuff out of your nose! It's time to sneeze!" So you take in a big breath of air, the muscles in your belly, chest and throat all squeeze really hard, you close your eyes, and then the air leaves your nose and mouth in a big noisy blast! [Squeaks sneezes and sniffles] Which hopefully clears all those irritating things out of your nose.

Some scientists study sneezes and they found that sneezing can send air flying out of our noses and mouths at over 100 kilometers per hour. That's as fast as some race cars. And sneezing is what's called a reflex. A reflex is something that your body does without you having to think about it. Blinking is another kind of reflex, when dust and other little things start to bother your eyes, and so is coughing if something is tickling your throat. Reflexes help protect our bodies from getting hurt or becoming sick, so sneezing helps you keep healthy by clearing out the inside of your nose. If you didn't sneeze, some of the particles or germs inside your nose might move deeper inside your body and those might make you sick. A nice big sneeze also helps smooth out all those little hairs inside your nose and spreads your own fresh mucus inside your nose to get it ready to trap more particles.

But when you sneeze, don't forget to cover it up because air isn't the only thing that leaves your body when your nose starts to go off. Sneezing also blasts saliva or spit and a lot of germs from our mouth into the air around up. Some scientists think that germs launched by a sneeze can travel about 60 meters, which is over half the length of a football field. So when you sneeze, it's important to keep those germs from spreading by putting something in front of them. If you don't have a tissue handy, sneeze into your elbow, and don't forget to wash up with soap and water afterwards. And remember, sneeze safely and keep healthy.

Thanks for joining us on SciShow kids. Do you have a question about how our bodies work or anything else? Get some help from a grown up and leave us a comment below or write us an email at kids@thescishow.com. And we'll see you next time.

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