Introduction: Germ Fighting for Kids

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One of the first life lessons a child learns is that 'coughs and sneezes spread diseases'. Most kids know that 'germs are bad' and that washing hands is important, but I wanted to teach the real science of our immune system. I felt that by equipping kids with decent scientific understanding, they'd come to see a) when you're sensible, germs aren't too scary at all, b) despite being young, they are capable of understanding some pretty high-level scientific concepts and c) our bodies are incredibly impressive in how they work!

This lesson was run as 'Germ Ninjas': a hands-on Saturday club run by Science Oxford for children aged 5-9 and their families. It has been planned in such a way that a range of scientific concepts are introduced in an exciting and age-appropriate way. One thing that is important to me when planning and running clubs is that my audience can see that learning isn't just for children; the concepts in this workshop may have been new to many of the adults also and families were encouraged to work together.

This workshop was originally 90 minutes long without breaks. Our normal club set up is that families take part in a range of activities. For those of you wanting to replicate the club either at home with children or in the classroom, it is possible to select individual activities from the programme or to use the activities as springboards into other areas of study. This workshop includes activities that include scientific enquiry as well as crafting activities that nurture fine motor skills. All in all, this work shop is quite low-tech and requires little to no specialist equipment. All resources are easy to find either in the supermarket, high street or online retailers.

This Instructable features a breakdown of the activities I led along with the supplies needed to run them. I have also included some prompt questions and answers to help you challenge the most able and push higher level enquiry in your class. Throughout this Instructable, I have included scientific vocabulary in bold. Even though a vocabulary this extensive isn't a key part of the school curriculum for this age group, there's no harm in starting them early; you'd be amazed at the pride kids take in knowing fancy words!


Listed below are the supplies needed for each activity:

What are Germs?

A selection of toy microbes. The ones I used are made by GIANTmicrobes and can be purchased online from various retailers. I used the following microbes:

- Common cold

- Meningitis


- E-Coli

- Staphylococcus


Child volunteers (this is most effective when you have at least four children to help you demonstrate!)

Loose-weave net


Building Blood

Red water beads (pre-hydrated for at least 8 hours beforehand)

Lidded boxes (transparent are most effective)


Butter beans (UK) / Lima beans (USA) or white ping pong balls (for a longer-lasting blood model)

Red craft foam cut into chewing gum size pellets

Small zipper bags

Sticky labels

Pens/ pencils

Ooey Gooey Snot

3x 500ml beakers, containing each of

- Borax solution

- Water

- PVA glue



Green food colouring

Eucalyptus oil/ menthol essential oil

Small Beakers- disposable cups (please consider the environment here!)

Record chart (attached)

Teeny Tiny Germs

Shrinkable plastic

Pens/ pencils



Baking tray

Oven gloves

Pom Pom Germs



Pom Pom Makers

Googly Eyes

Liquid glue

Step 1: Activity 1: What Are Germs? Introduction

Supplies: Toy microbes

This discussion introduced the topic of germ fighting.

“Germs”is an umbrella term used to describe pathogens such as bacteria and viruses. Germs are everywhere, and most of the time they do us no harm as our bodies protect us against any invaders! It’s very healthy to have some germs in our bodies, and being exposed to germs in small amounts helps us to stay fit and healthy. Our immune systems are strengthened in this way.

However, bacteria and viruses multiply quite quickly in the right conditions, and very often our bodies are the perfect environment for them to grow in numbers! When their numbers overwhelm our bodies’ defences, we get ill.

Imagine our immune system is made up of tiny toy soldiers. Each soldier could probably wipe out a few germs fairly easily, but if there are too many germs (or not enough soldiers for that matter!) then they will have a very difficult job indeed. *See attached PowerPoint for a visual to demonstrate this*

There are lots of different types of germs that you might have heard of, including:

Common Cold- This is a virus that we’ve probably all had loads of times! For most people, colds are nothing serious and will linger for a week or so, giving you a cough, sore throat or a runny nose. The cold virus is constantly mutating (changing), which is why people say ‘you can never catch the same cold twice’. It is incredibly easy to spread and catch colds, and whilst they’re generally harmless (if only a bit miserable), hand washing makes a huge difference to whether or not you become ill. Think about everything you touch in a day: door handles, banisters in school, the toilet, food, your mouth! Cold viruses will stay alive on surfaces for a short amount of time, but need a human body to really thrive. So wash your hands! You might be wondering why we seem to catch so many more colds in the winter than in the summer. The reason for this is all to do with body temperature. Our bodies are good at staying around the same temperature: this is called our core body temperature. We sweat and shiver, depending on our environment, to help keep our core temperature the same (the scientific word for this is homeostasis). But our noses, because they stick out, can be a little bit cooler in the winter, and this slightly lower temperature is perfect for the cold virus to breed.

Meningitis- Meningitis can be caused by bacteria or viruses and it affects the brain. There are vaccines available that protect against some kinds of the illness. You might have had these vaccinations yourself, as it is standard for them to be offered to babies and some offered when you’re in school. Vaccines are a little bit like showing your immune system a wanted poster and then training them in combat, telling them 'if you see this invader, attack it before it hurts you and this is how you do it!'

MRSA- This dangerous bacterium is often referred to as a ‘super bug’ because it is resistant to a lot of the antibiotics that are widely used. The toy version has a cape, but this is just for show! Antibiotics are used to treat bacterial infections, and most can be successfully treated. However, if you take antibiotics when your body doesn’t need them, it can be bad for you as you can become resistant, meaning the drug won’t work in the future. About 1 in 30 people will have MRSA living on their skin (that means there’s likely to be someone in this room with it!) but it is harmless as the number of bacteria will be low.

E-Coli- Healthy bodies may have e-coli living in their guts( that means your stomach and intestines). But in large amounts, E-Coli can lead to food poisoning. This means sickness and diarrhoea, which can become serious. Food hygiene is really important, so handwashing, cooking in a clean kitchen and cooking food properly is very important.

Staphylococcus- Staph infections are caused by bacteria and normally affect the skin. That’s why it’s important to keep wounds clean. Lots of wounds on the skin, such as grazed knees and paper cuts are in themselves harmless, and will heal without any help in no time at all… In our next task, we will learn how this happens.

Prompt Questions:

Q: Who here has ever had an ear infection? Do you know what causes them?

A: Ear infections can be caused by viruses or bacteria. When the doctor takes a look, it’s not always obvious what has caused it. If you’ve had a rough cold, the chances are the virus has spread. Some ear infections are viral, meaning antibiotics won’t do anything. Doctors may just send you home to rest and stay hydrated and, if you have a virus, this should do the trick. If you have a bacterial infection and take antibiotics, you will probably feel better in a few days, but you should always finish the whole course of medication. This is because you will still have bacteria in your body. If you don’t get rid of them all, they will multiply and can make you ill again!

Q: Germs sound quite terrifying! Should we be scared?

A: Not at all! For the most part, germs do us no harm. You just have to be sensible: prepare your food in a clean environment, wash your hands (especially after going to the toilet!) and do your best not to cough and sneeze on others when you have a cold. We have very successful treatments for diseases caused by germs, and so in 2019 your chance of becoming seriously ill are much, much smaller than they were a hundred or so years ago. In fact, some scientists are wondering whether we’re too clean! Because we know more about hygiene, people are more careful when it comes to exposing themselves to germy things. Exposure to small amounts of germs is a good thing and, as we saw earlier, can help to make our bodies stronger. On average, people have more allergies these days when compared to previous generations. Some scientists think this is because, in an effort to be clean and healthy, we aren’t giving our bodies the chance to build up their strength against nasty germs. So play outside, climb trees and don't be afraid to get a little bit muddy. It won't kill you and may even make you healthier!

Step 2: Activity 2: Scabs

Supplies: Child volunteers, loose net, marshmallows

Blood contains many things and some of the main things are:

Red blood cells, which transport oxygen around the body

White blood cells, which work for our immune system, helping to fight infections and

Platelets, which help blood to clot.

We’re going to demonstrate this as a group. Children who would like to participate, please gather in a huddle. You are at the sight of a wound- a particularly nasty grazed knee. You are the blood, and you’re starting to clot to form a scab. Platelets stick together like glue to form a clot, which is why you’re standing so close together. Your blood also contains something called fibrin, which is a bit like this net that I’m going to gently place over you. This is what holds the scab together. Even if we try to keep wounds clean, some bacteria can get in. These marshmallows represent invading pathogens and they’re going to try to enter the wound. (I’m using hand sanitizer for cleanliness at this point!) White blood cells are clever and react to germs in a variety of ways. One such way has a fancy name- phagocytosis (pronounced fay-go-sigh-toe-sis). This is the name given to the process whereby white blood cells eat, or digest, pathogens. Who wants to eat some marshmallow pathogens?!

Prompt Questions:

*For a visual cue, show the zoomed-in image of blood in the attached PowerPoint*

Q: Does anyone know why we have blood?

A: It’s the body’s way of transporting oxygen and other nutrients to every organ of the body. Blood is carried in vessels, such as veins, arteries and capillaries and these can be found all over the body. Some are quite large (such as those in your heart, or the ones that are visible in your wrist) and some capillaries are so tiny you'd struggle to see them with the naked eye.

Q: One thing we all have in common, and have in common with many other types of animals is that our blood is red. There’s something in our blood that causes this; does anyone know what it is?

A: It’s something called ‘haem’ which is part of haemoglobin, an iron-containing protein that transports oxygen around the body. We get a lot of iron from our diets, and eggs, meats and fish are a good source.

Fun fact: Did you know that spiders’ blood is blue?

Q: We’ve just demonstrated why it’s important to leave scabs alone when they have formed. What might happen if I remove this fibrin net and move my platelet people apart?

A: You risk reopening the wound. You’ll know this happens if you’re bleeding, but it's not just about what's coming out that you need to think about! You also risk letting pathogens in. Too many pathogens and your body's white blood cells will be overwhelmed. This is how infections, such as staph infections, start!

Step 3: Activity 3: Building Blood

Supplies: Lidded boxes of red water beads, butter beans/ lima beans, red craft foam, small zipper bags, sticky labels, pens

Blood is really important and can even be donated! Donated blood is used for patients that either have lost a lot of blood, or if their own blood isn’t working for them. Blood has different types, and these are known as ‘blood groups’. If everyone in the room were to give a little bit of blood, to the naked eye it would all look the same. But under a microscope, there’s a whole other story! Our blood group is determined genetically, which means that it’s something we get from our parents. Our blood group is made up of two genes: one from mum and the other from dad. You might know your blood group if you’ve ever had treatment in hospital, and grown-ups may have learnt theirs if they’ve donated blood in the past. *Please see the slides attached to this Instructable for a table detailing inheritance of blood groups.*

Build your blood using:

Red blood cells: red water beads (your body has lots of these)

White blood cells: butter beans (just a few of these) *Do not eat*

Platelets: Craft foam in small pieces, about half the size of your little finger.

You can then create a label for your blood!

Fun Fact: Did you know that in the average healthy adult, there is only 1 white blood cell for every 600 or so red blood cells?

Prompt Questions:

Q: What would happen if we had too many or not enough white blood cells?

A: Blood tests can tell how many white blood cells you have. A tiny tube of blood can give a clear picture of what’s going on in your whole body, which is a good thing as it would take forever to count them all! If you don’t have enough white blood cells, you may struggle to fight infections. If you have too many white blood cells, you might have an illness that needs to be treated. With white blood cells, it isn’t a case of the more the better. As white blood cells fight infections, having too many can mean the body starts attacking healthy cells. Like a stampede of elephants, those white blood cells wouldn’t be so selective about what they’re trampling all over, and healthy bodies can get damaged in the process! Smoking often raises a person’s white blood cell count, which is another good reason not to smoke!

Step 4: Activity 4: Ooey Gooey Snot

Supplies: Containers of water, PVA glue, and borax solution on each table. Green food colouring, eucalyptus/menthol essential oils, paper or washable cups, lolly sticks, pipettes, spoons, record chart (photocopies- attached)

Prompt Question to Start:

Q: Our body is covered by something really important that does an epic job of stopping pathogens from getting in. What is it?

A: Skin! It’s our largest organ and acts as a barrier to the outside world. It’s important to look after your skin, and your skin does a great job of looking after you. So be kind to your skin; stay hydrated, moisturise and avoid sun damage!

Sometimes pathogens can enter the body in other ways; skin doesn’t seal our whole body shut like a giant morph suit! Our eyes, noses and mouths are open to the world, and sometimes germs can want to sneak in. Snot is gross but incredibly important. It is mucus, which lives in our noses and throats and it ‘catches’ germs. We can either blow our noses to remove germ-filled snot, or it gets swallowed! Snot also contains a special chemical (an enzyme) called lysozyme (pronounced lie-so-zime). Lysozyme helps to break down germs and kill them before they can do us any harm. You’ll also find lysozyme in tears!

When we are ill, we produce more mucus. This is why, when you have a cold, you’re constantly sneezing, wiping your nose and have a phlegmy throat! The saying ‘coughs and sneezes spread diseases’ is true. Whilst sneezing on someone, or touching something someone has coughed on, probably won’t do you a huge amount of damage, coughs and colds are spread this way and are very contagious. Earlier, we learnt that having too few white blood cells would mean a person would be more likely to pick up infections. Most people’s immune systems have just enough white blood cells, and can fight off the germs they encounter each day, but some people who have weaker immune systems (either because of another illness or sometimes because they're very young or very old)can catch illnesses more easily. That’s why it’s still important to ‘catch it, kill it, and bin it!’ and wash your hands regularly, even if you’re one tough cookie.

We’re going to do a test in which we figure out how to make the most realistic snot. You will be given the materials you need, but it's up to you to experiment with different quantities. If you have made slime before, you might be familiar with some of the materials we are using.

PVA glue

Borax solution


Green food colouring (few drops)

Eucalyptus/Menthol oil (few drops)

Create different mixtures, using the PVA glue, borax solution and water in different quantities. You should keep the amount of fragrance and food colouring (just a few drops) the same in each mixture. You will notice that changing the quantities of the ingredients will lead to the finished product looking different. In the interests of a fair test, we are going to keep our method the same, only changing one variable (quantity of ingredient) at a time. I’m not going to tell you how much of each thing to use, it is for you to test out. It’s a bit like the challenge on The Great British Bake Off, except really, really gross:

1. Mix PVA glue and water and stir until fully incorporated

2. Add a couple of drops of green food colouring and fragrance oil and stir until mixed

3. Add borax solution and quickly stir with a lolly stick or spoon

On your sheet (attached), record the quantities of each ingredient used in each round and jot down the result. What does your snot look like? What is its texture like? Is it solid or liquid?

Your challenge is to create the most realistic snot, and be able to explain to the group how you achieved it!

Something to think about: Why might we have added the fragrance oil to our snot slime? Think about how it is affecting your body...

Step 5: Activity 5: Teeny Tiny Germs

Supplies: Shrinkable plastic, pens/pencils, scissors, oven, baking tray, oven gloves

Did you know that we are more bacteria than human?! There are around 39 TRILLION bacterial cells in the human body, compared with a measly 30 TRILLION human cells. This just goes to show that bacteria aren’t all bad, and most of the time we don’t even think about them being there.

Earlier, we looked at soft toy pathogens, and saw that whilst they were all different, they had some things in common. Bacterial cells have different parts, like ‘body parts’ which each do a different job:

· The cell wall keeps the bacteria together, a bit like its skeleton, whereas the plasma membrane is like its skin, protecting the cell against harm.

· The flagellum is like a tail, which helps it to move.

· The DNA is like a long tangle of string, which contains all of the bacteria’s genes.

· Pili are like tiny hairs which help the bacteria stick to things.

· Ribosomes are like the bacteria’s ‘kitchen’ where the nutrients that help them survive are made.

Bacteria are too small to see with the naked eye, and in order to see them, we need to use microscopes. We’re going to have a go at making teeny tiny germs, using a special kind of plastic which shrinks at high temperatures. Simply draw your bacteria on the rough side of your plastic and cut it out using scissors (this part is up to you). When you get home, bake it in the oven on a metal tray at 175°C/ Gas 3/ 350F until the plastic curls up and then flattens again. This normally takes about a minute, so keep an eye on it! When you take the tray out, press another tray (or something else with a heat-proof flat bottom, such as a mug) on top of your bacteria to help it cool flat. It will be around 7x smaller now!

Step 6: Activity 6: Pom Pom Germs

Supplies: Yarn, Scissors, Pom Pom makers, googly eyes, liquid glue

Pom Pom Germs are a great, quick craft activity to remind you that germs aren't to be feared! In fact, we're going to make them very, very cute.

1. Take your pom pom maker and line up the two halves so they slot together.

2. Wrap yarn around one half of the pom pom maker until it is almost full.

3. Repeat on the other side.

4. Close your pom pom maker and clip it shut. Using scissors, cut between the two halves.

5. Using a length of yarn about 6 inches in length, tightly tie your pom pom together between the two halves of your pom pom maker.

6. Open up your pom pom maker to release your finished pom pom.

7. Trim away any excess yarn (give him a nice hair cut!) and finish him off with a couple of googly eyes.

In our workshop, kids made their pom pom germs into key rings, earrings and hair ties!

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