Baby, Toddler, Child
31st Jul 2020

Through infancy, toddlerhood, childhood and all the way into their adult lives, your little one’s immune system is busy at work to keep unwanted bugs and germs at bay.

You may be wondering, which parts of the body make up their immune system, how does your child’s immunity develop over time, and how might you help to support it?

Your little one’s immune system is incredibly intricate, so there’s a lot to unpack. Here are some helpful links to help you navigate the content on this page:

If you have any concerns about your child’s health or immune system, talk to a suitably qualified health professional.

What Is The Immune System And How Does It Work?

The immune system is our very own, inbuilt defence mechanism that is in charge of shielding our bodies from unwanted bugs and germs.

It is a diverse and complex system, made up of specific organs, cells and messengers. These different players work together to spot foreign germs and destroy those that may cause us to become sick (1).

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Why Is The Immune System Important?

Put simply, the immune system is our first line of defence against foreign invaders (a.k.a germs).

The many organs, cells and messengers that make up the immune system work together to detect when invaders enter the body. They find the foreign germs and fight against them to keep us healthy.

Foreign invaders are known as pathogens (6). Some pathogens may cause us to become unwell, including the 200 or so bugs associated with the common cold. Anything foreign that causes the body to mount an immune response is called an antigen (6).

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Which Body Parts Make Up The Immune System?

There is a range of different components that contribute to healthy immune system function and each has its own important and specific roles to perform. Some of these include:

White Blood Cells

When it comes to the immune system, white blood cells are some of the most well-known players.

That’s because they perform the important job of finding and attacking unwanted bugs and germs that may enter the body (2,3).

Although there are many different types of white blood cells, all of them are made in our bone marrow, which is the spongy tissue found inside our bones.


Our white blood cells produce antibodies to help us fight off foreign germs and to assist with other immune responses (3). These antibodies are very clever and are able to spot the bugs and alert the body, stimulating an immune response (2).

You may like to think of antibodies as the bounty hunters of the immune system, seeking out and destroying foreign invaders.

They do this by recognising substances on foreign microbes’ surfaces known as antigens. When our antibodies detect these antigens, they mark them for destruction and join the attack against them alongside other the important cells, proteins and chemicals that make up the immune system (2).

The Lymphatic System

The lymphatic system is a network of tissues and organs that work together to remove waste from the body.

One part of the lymphatic system that you may have heard of is the tonsils. Not only are they home to lots of white blood cells, but their location in the throat also helps to stop germs from entering the body through the mouth and nose (4).

Interestingly, it also includes part of the digestive system. It’s involved in the immune responses that occur at the mucus membranes, such as those that line the intestines (3,5).

In addition to helping to remove toxins from the body, the lymphatic system also serves as a transport system for immune cells, including white blood cells, moving them between tissues and through the bloodstream (5).

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What Is The Difference Between Innate And Adaptive Immunity?

Did you know that there are two different sides to your immune system, known as adaptive and innate immunity?

Innate Immunity

Established in the womb, innate immunity is the part of the immune system that we’re born with.

Our innate immunity includes physical barriers, like our skin and the mucous membranes that line our nose, mouth, throat, lungs and digestive tract.

Mucous membranes play a protective role for these parts of the body, which regularly encounter foreign substances in the air we breathe and the food we eat. They do so by trapping dirt, dust and germs to be flushed away. The mucous membranes are also home to important immune cells (6,7).

Adaptive Immunity

The body’s ability to develop immunity over time is called acquired or adaptive immunity (8). In contrast to innate immunity, adaptive immunity grows as the body is exposed to pathogens.

When the immune system mounts a response against an invading germ, it remembers the attack. This is thanks to some white blood cells known as ‘memory cells’.

Our memory cells form an important part of our adaptive immunity, keeping a record of all the bugs that the body has fought off in the past (9). So, when the same germs try to invade again, the body may be able to respond more efficiently (9).

Adaptive immunity is one of the reasons why adults experience an average of 2-4 common colds each year, compared to 5-10 for young children who have been exposed to fewer bugs (10).

So you may wonder, if adaptive immunity helps the body respond to familiar germs, why may we experience some illnesses more than once?

The common cold is one example of this. There are more than 200 different bugs that may cause a common cold and unfortunately, when your body develops immunity to one of these bugs, it does not aid your immune response against all of the others (8).

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How Does The Immune System Develop Over Time?

We know that immunity grows overtime. So, what does this mean for your little one, whose immune system is still in the early stages of development during pregnancy, infancy and early childhood?

Your Baby’s Immune System During Pregnancy

During pregnancy, your little one grows from a tiny bundle of cells into a fully formed baby. As they grow and develop over the nine months, so too does their little immune system.

Antibodies are one part of this and are passed from a mother to her child in the womb (11,12).

A child’s birth may also be an important time for their immune system. During birth, bacteria is passed from the mother to her newborn, which helps to build the colony of healthy bacteria in the baby’s gut (11,12). This process varies depending on whether the child is born by vaginal birth or C-section and is part of the development of their healthy microbiome.

Learn more about the relationship between your child’s microbiome and their healthy immune system function.

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Your Child’s Immune System During Infancy And Childhood

During infancy, your child’s immune system is immature because it is yet to encounter many germs. But, as they are exposed to different bugs over time, their adaptive immunity develops (11,12).

A baby is born with the antibodies that were passed to them from their mother in the womb.

And, as their little immune systems fight of different bugs and germs, they produce their own antibodies for them to use in the future (11,12).

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What Factors May Affect Your Child’s Immune System?

As with many aspects of your child’s health and wellbeing, their immune systems may be affected by several lifestyle factors.

If you have any concerns about your child’s immune system health, talk to your health professional. During this consultation, you may wish to discuss some of these factors with them.


Like in pregnancy, during breastfeeding a mother passes antibodies and nutrients to her baby. This aids the development of their little immune system (11,12).

The Australian Government’s Infant Feeding Guidelines advise that, where possible, babies should be exclusively breastfed until they are around 6-months-old.

It also recommends that children continue to be breastfed while solid foods are introduced, until their first birthday at least (13).

Once they begin eating solids, you can help to support their healthy immune system with a balanced diet as outlined in the Australian Guide to Healthy Eating.

Discover which foods to include in your child’s diet to support their healthy nutrient intake.

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Ensuring they get enough sleep is important for supporting your child’s healthy growth and development. This is, in part, because adequate sleep supports immune system health and function (14,15).

Explore the recommended sleep times for children by age here.

If you have any concerns about your child’s sleeping habits, talk to your health professional.

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The immune system plays a demanding role in helping to maintain our health and wellbeing. So, like other important bodily functions, it requires support from several nutrients.

These nutrients are usually the result of a healthy and balanced diet full of fresh fruit, vegetables, whole grains and protein.

To help maintain your child’s healthy immune system function, it’s important to ensure they get their Recommended Daily Intake of vitamins and minerals.

Discover the key nutrients that support a healthy immune system and which foods contain them here.

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The Microbiome 16,17,18

Did you know that our bodies are home to a 100-trillion-strong colony of bacteria that influence our health? Made up of all the microorganisms that live in and on the body, this is known as the microbiome.

The microbiome has many functions in the body, including helping us to absorb nutrients, regulating our immune system and defending us against unwanted bugs and germs.

The gut is home to approximately 70-80% of the body’s immune cells and a healthy gut microbiome supports immune system health (18).

A healthy microbiome also supports some of the body’s first lines of defence: the mucous membranes that line the nose, mouth and throat.

You may be able to help maintain your child’s healthy microbiome by supporting their healthy bacteria balance with a probiotic. If you’d like to learn more about probiotics, you can find more information here.

If you have any concerns about your child’s microbiome, talk to your health professional.

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Immune System Nutrition: The Importance Of A Healthy Diet

Ensuring your child eats a wide variety of healthy foods is one part of supporting their overall health and wellbeing. This also includes supporting their immune system health and function.

Vitamins And Minerals That Support Your Child’s Immune System (And Where To Find Them) (1,19)

Different nutrients support the immune system in different ways. So, by serving your child a variety of fruits, vegetables, proteins, dairy products and whole grains you may help to ensure they receive their Recommended Daily Intake of each.

If you have concerns about your child’s diet, talk to a suitably qualified health professional. You may also like to discuss the following nutrients with them.

Vitamin A

Vitamin A supports the development and function of white blood cells and antibodies, which detect and attack unwanted germs and bugs in the body.

This nutrient also plays a role in maintaining mucous membrane health, which is your child’s first line of defence against foreign invaders.

Dietary sources of vitamin A include:

  • Carrots
  • Sweet potato
  • Spinach
  • Capsicum

These foods contain betacarotene, which can be converted into vitamin A in the body.

Vitamin C

Perhaps one of the most well-known vitamins for supporting immune system health, vitamin C aids the body’s response to foreign invaders.

Dietary sources of vitamin C include:

  • Berries
  • Kiwifruit
  • Tomatoes
  • Citrus fruit such as oranges and lemons

Discover the benefits of vitamin C for children here.

Vitamin D

Vitamin D plays an important role in normal, healthy immune responses and supports immune cell production.

Did you know that vitamin D is affectionately known as the ‘sunshine vitamin’? That’s because our bodies are able to produce it when our skin is exposed to the sun.

Our total vitamin D levels include a combination of dietary intake and sunlight exposure. In Australia, we get most of our vitamin D from the latter.

Explore the signs and symptoms of inadequate vitamin D levels here.


Zinc is necessary for mounting a healthy immune response against invading pathogens because it plays a role in immune cell development and function.

When the body has adequate zinc levels, our immune response is regulated and functions optimally.

Dietary sources of zinc include:

  • Meat
  • Dairy products
  • Cereals
  • Seafood

Learn more about why zinc is important for babies and children here.

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Good Hygiene Habits To Help Prevent The Spread Of Germs

While your child’s immune system is hard at work to keep them healthy, there are some things you may do to help prevent the spread of germs. Teaching your child the following good hygiene habits may help to support their immune system and reduce the frequency of illness in your household.

Practice Thorough Hand Washing

One of the ways that bugs spread is by touching something with germs on it and then touching our face or using our hands to eat. Explain this to your little one and that an easy way to prevent this is by washing their hands.

Teach them to wash their hands effectively by using warm, soapy water, lathering for at least 20 seconds, and drying their hands with a clean hand towel.

A hand sanitiser may also be useful for cleaning your little one’s hands when soap and water aren’t readily available. But make sure it contains at least 60% alcohol (20).

Limit Face Touching

Try to dissuade your child from touching their eyes, nose or mouth until their hands are nice and clean. This includes eating, blowing their nose and rubbing their eyes.

What Not To Share

Although sharing is an important skill for children to learn, it is also important to teach them not to share things that come into contact with their mouth. Explain to them that by not sharing straws, cups, cutlery and bottles, they may help to prevent the spread of germs.

Coughing And Sneezing Control

Explain to your little one that when the cough or sneeze, the germs they release go into the air that others breathe in. Teach them that by sneezing into a tissue and discarding it promptly as well as coughing into their elbow, they may help to reduce the spread of bugs and germs.

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Tips That May Help Support Your Child’s Immune System

As a parent, you may be wondering what you can do to help support your child’s immune system health. The following tips may help to maintain their healthy immune system function, so it can continue to fight off bugs and germs:

  • If possible, breastfeed your baby for at least the first six months of their life (19)
  • Ensure your child gets their recommended hours of sleep each night
  • Support your child’s nutrient intake with a healthy, varied diet
  • Encourage your child’s good hygiene habits by explaining to them how germs spread and teaching them thorough hand washing techniques
  • If you have any concerns about your child’s immune system, talk to a health professional

Remember, your little one’s immune system is their very own inbuilt defence mechanism. Designed to ward off unwanted bugs and germs, it’s very clever and develops over time. It’s normal for your child to experience a common cold every now and then as their immune system learns and adapts with exposure.

If you have any concerns about your child’s immune system health or function, take them to see a doctor who will be able to assess their individual circumstances and needs.

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If you’ve found this information useful, you may enjoy the following:

How To Teach Your Little One Healthy Hygiene Habits 

This Is How Zinc Helps Support Your Child’s Healthy Immune System