Wash your hands! How many times each day do you hear those words? Of course, it’s important to wash your hands regularly to stay healthy and clean. Washing your hands gets rid of germs that can cause you to get sick.

But can germs also be good? You bet they can! Read on to learn more about germs and how they can be both bad and good.

If you’re wondering exactly what germs are, don’t worry. They’re not alien forces or “cooties.” They’re actually tiny living organisms. They’re so small, in fact, that you need a microscope to see them.

Germs can creep into our bodies in many different ways without being noticed. Although some can cause sicknesses and infections, such as sore throats, ear infections and cavities, others are helpful to our bodies. That’s right. Some actually are helpful!

The four main types of germs are bacteria, viruses, fungi and protozoa. In today’s Wonder, we’ll concentrate on bacteria.

You might be surprised to know that your body contains over 100 trillion bacterial cells. That’s 10 times the number of human cells! How can your body hold that many bacterial cells? Don’t forget how tiny they are: a single bacterium is one-thousandth the size of a regular human cell.

Some of the bacterial cells in your body may cause you to get sick from time to time. However, many of those bacterial cells work with your body to keep it balanced and healthy.

For example, the good bacteria that live in your intestines help your body make the best use of the nutrients in the food you eat. They also help turn what’s left over into waste. Without these good bacteria, your body couldn’t efficiently process the food you eat.

Scientists also use bacteria in other important ways. For example, some medicines and many vaccines are made from good bacteria.

Researchers have been studying good bacteria more thoroughly in recent years. Some believe that using antibiotics too often might kill off good bacteria, leading to obesity due to inefficient digestion.

Other researchers believe that good bacteria may have a wide variety of benefits. Studies have shown that good bacteria may help prevent diabetes and asthma, make the immune system function correctly and even ward off certain types of cancer. Bacteria living on your skin might also help prevent infections.

Researchers believe that drug companies may one day sell medicines that treat illnesses by increasing the amount of particular types of good bacteria in the body. While these types of drugs are likely years away, food manufacturers have already started making foods intended to increase the good bacteria in the body.

These products — from yogurt to cereal to drinks — contain probiotics, which are good bacteria that aid in digestion and may also help fight bad bacteria. Early research suggests that probiotics may help prevent colds and the flu, treat diarrhea, reduce certain types of cancer and even prevent certain types of skin problems.


58 Join the Discussion

1 Star2 Stars3 Stars4 Stars5 Stars  (30 votes, avg. 4.10 out of 5)
    • Thank YOU for visiting Wonderopolis today and for letting us know what you thought about today’s Wonder of the Day®, Dylan! :-)

    • Happy Monday, Mrs. Denning’s Class Grade 2! We’re glad you visited Wonderopolis and let us know what you liked learning here today! Science Wonders are super fun (so are all the other kinds of Wonders, too)! :-)

    • Thanks for letting us know you learned that germs can be GOOD for you, Jacob! We sure appreciate you hanging out in Wonderopolis today and leaving us this super comment! :-)

  1. I loved today’s wonder. I did not know that our bodies have over 100 trillion germs 10 times more than our blood cells. I knew that some bacteria was good for you, but I did not know how many or what kind. I also think tomorrow’s wonder will be about something that’s very delightful to people.

    • We think it ROCKS that you learned some new facts about germs by exploring today’s Wonder, Megan! Thanks for being a GREAT Wonder Friend and letting us know you loved today’s Wonder, too! :-)

    • That’s an AWESOME guess about today’s Wonder, Yaseli! We can’t wait to visit tomorrow’s Wonder to see if your guess was correct! :-)

  2. Hi, wonder. I’m at school right now and I wonder if germs are good for you. Are they? I just wanted to know if you are the smartest to know, if you are the smartest website, because you’re very smart to me because you know almost everything. :-)

    • Hi, Simon Bird! Thanks for leaving us this great comment today! We hope you learned some cool facts about germs and how, even though some are not good for our bodies, others can be very helpful! We don’t think we’re the smartest website, but we sure do LOVE to WONDER a lot! Thanks to great Wonder Friends like you, we always have more, and more, and MORE things to explore and discover together here in Wonderopolis! :-)

  3. I did not know bacteria was good. I thought it was all bad. I did not know some bacterias could keep us healthy. I like how you can take videos from youtube to show us information.

    • Thanks for letting us know what you like about visiting Wonderopolis, Lucas! We search high and low to find the best videos to accompany each Wonder of the Day®! :-)

  4. Dear Wonderopolis,
    That was an interesting wonder! I think tomorrow’s wonder is about the ocean.
    A special shout out to my friends Katie, Eleni, and Isabel. YOU ROCK!
    Paige ;)

    • Hello, Paige! What a GREAT friend you are to tell Katie, Eleni and Isabel how much they mean to you! Thanks for checking out today’s Wonder about germs! :-)

  5. This was very helpful. The link of the book to explain more was cool and very informative. Wow, I did not expect for some germs to be good. I learned that our bodies have over 100 trillion germs, 10 times more than our blood cells. I believe that tomorrow’s wonder of the day will be about dairy products. What was your personal favorite wonder ever created? Are there any specific names of germs that are good for you?

    • WOW, Kate! That sure is a lot of cool stuff you learned by exploring today’s Wonder of the Day®! Thanks for sharing! We like ALL 484 of the Wonders so far! They are ALL our favorites! We also really like it when our Wonder Friends (like you) leave us comments to let us know they visited and to share all the great facts they learn here in Wonderopolis! :-)

    • You’re so awesome for letting us know what you thought about this Wonder of the Day®, Bridget! Thank you so much for WONDERing and learning with us today! :-)

    • Hello, Joshua! This is a Wonder of the Day® because an awesome Wonder Friend (just like you) WONDERed about germs and if some germs can be good for you! What do you WONDER about? You can tell us by clicking on the “nominate” link at the top of every page in Wonderopolis and filling in the boxes! It’s really easy and really fun to share what great ideas you have for future Wonders of the Day! :-)

  6. This wonder will help us to be more aware of reading labels. Eating foods with probiotics may keep us from getting sick. Can kids with allergies have foods that contain probiotics? We thought this video was a great one that contained lots of good information!

    • Thanks for letting us know all the cool things you learned by exploring this Wonder about GERMS, Mrs. Watson’s Class! We don’t know if kids with allergies can eat foods containing probiotics. That’s a GREAT question, though! Maybe we can all do a little bit more WONDERing about it! :-)

  7. Dear Wonderopolis,

    We LOVED this wonder! We have been exploring and learning about germs and diseases as part of our Physical Health unit. We’re still wondering a couple of things:

    1. Can bad germs become good germs?

    2. Are there more bad germs than good germs?

    Thanks for helping us wonder.

    • Those are AWESOME questions, Mrs. Armfelt’s Third Grade Class! We’re happy that you guys liked this Wonder of the Day® about germs, and also that you were able to learn some new things that will help you with your Physical Health unit! We will all have to do a bit more WONDERing about your questions! Part of the fun of Wonderopolis is that we all get to learn a few new facts about things that make us WONDER, then we get to WONDER even MORE on our own as we discover even MORE facts! :-)

    • You’re welcome, Michael! We’d like to thank YOU for visiting this Wonder and for leaving us a cool comment to let us know you were here! :-)

    • We think it ROCKS that you enjoy learning about germs, ASD, and also that you visit Wonderopolis and leave us awesome comments! :-)

    • We’re glad you hear you liked this Wonder, ASD! Thanks so much for telling us and for being a GREAT Wonder Friend! :-)

  8. Helllllloooooooo!!!!!!!!!!!! This is a great wonder! p.s. this website is a great one, we love it!

    • Your comment just made our day a bit more WONDERful, Mrs. Armfelt’s third grade class! We appreciate you letting us know you liked today’s Wonder about germs! :-)

    • Yes, germs (like bacteria and fungi) can hide in our shoes, Mrs. Armfelt’s 3rd grade class! That’s what causes some people to have stinky feet and get things like athlete’s foot! Thank you for being AWESOME Wonder Friends and asking so many great germ questions today! :-)

  9. Hi Again!!!! I’m the one who commented on 2 other things. I think it is sooooooo crazy how some germs and bacteria are good for you. I thought all bacteria was bad for you. I am astounded about this, thanks! Please post another awesome video tomorrow!!!

    • WOW! We really enjoyed all the comments you left for us, Abby! We know it means you learned some FUN facts about things you WONDERed about today! Thanks for being a SUPER Wonder Friend! :-)

    • Thank you so much for letting us know how you feel about Wonderopolis, Hellen! We appreciate your honest opinion and hope you’ll give learning in Wonderopolis another try sometime really soon! :-)

    • We’re REALLY HAPPY that you think Wonderopolis is interesting, Taylor! Thanks for being such an AMAZING Wonder Friend! :-)

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Have you ever wondered…

  • Can germs be good for you?
  • What are the four major types of germs?
  • What are probiotics?

Wonder Gallery

Try It Out

Want to learn even more about bacteria? Read Dr. Mel’s fun online book called Bacteria Galore by Sunday at Four! We’ll bet you never knew there was so much to learn about bacteria.

You can also play one of these fun bacteria-related games online:


Still Wondering

Science NetLinks’ Antibiotic Attack lesson explores how the human body may not work as well, or at all, if harmful germs are able to get inside it.


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