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Jessi: Here's a handy tip for those of you who happen to have a human body: when something comes out of your body on a regular basis, your body's probably got a good reason for getting rid of it. Like how sometimes if there's too much gas in our stomachs, it'll just go right back up the way it came in, and [Squeaks burps] and generally speaking, the same goes for whatever you might find coming out of your nose.

Our noses get rid of slimy, gooey, and sometimes crusty stuff. You know what I'm talking about: boogers. And yeah, boogers are pretty gross, but keep in mind that almost everything that makes up our bodies has a purpose, that is, until it's time for it to leave. So where do boogers come from and why are they there? Let's start with what happens when you take in a breath.

When you breathe in or inhale, you're not only pulling air into your lungs, you're also taking in a lot of what's floating around in the air; stuff that's too small to see, like dust and dirt, pollen from plants, smoke and other kinds of pollution, and germs. If these things get into your body, they could make you sick, but thankfully, your body has a powerful weapon to help trap these things before they can get too far, and that weapon is mucus. Yep, the same gooey slimy snot that clogs up your tissue and runs out of your nose when you have a cold or allergies, that stuff has a purpose.

When you breathe in and out, air moves through your mouth and nose and down to your lungs. These parts of your body make up your respiratory system. The job of your respiratory system is to help your body get the oxygen it needs from the air. And all of the parts of your respiratory system are lined with a thin layer of mucus, even if you're not sick.

Your body makes a lot of mucus, but usually you don't notice it, that's because the mucus is normally very thin and watery. It helps keep the parts of your respiratory system moist and healthy, but it's also really really sticky, and as the air you breathe passes over it, many of the teeny tiny particles in the air, the germs, dust, and other irritating things, stick to it and get trapped. Then, it's time to take out the trash.

Little hairs in the back of your nose and lungs called cilia act like brooms, sweeping the mucus to your throat where it gets swallowed and goes right to your stomach. But don't worry, the inside of your stomach is full of chemicals that destroy all of the germs and other stuff, so you don't get sick. But what about that stuff up your nose?

Well sometimes the air you breathe in is really dry, and when you breathe in a lot of dry air, the mucus that lines your nose, instead of being thin and watery gets dry and crusty, kind of like what happened to mud when it dries out. The hard things left behind, dried up mucus and dirt, are the boogers, the stuff stuck in that mucus when it dries out can change the color of what comes out of your nose.

Sometimes mucus has tiny bits of blood which makes it brown, and sometimes your body sends cells to kill the germs in the mucus, and these cells have chemicals in them that can make the mucus kind of green or pink. But no matter what's in them, blow your nose in a tissue, don't pick it.

Boogers are full of germs that were trapped by that mucus and some of those germs could still spread disease. After all, the boogers are there because mucus has kept that stuff out of your body. So keep a tissue handy and blow your nose. And wash your hands thoroughly afterwards, good manners are also good science.

Thanks for joining us on SciShow Kids. Do you have a question about how something works in your body, ask an adult to help you leave a comment below or email us at kids@thescishow.com. And we'll see you next time.

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