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What is my immune system and why is it so important?

23 Nov 2022 • 3 min read


When your immune system is in tip-top condition, you probably don’t even notice it working away to protect you around the clock.

However, you’ll know when there’s something wrong as your immune system is your body’s in-built defence system against illness and infection. If you feel good today, thank your immune system (and give yourself a pat on the back for looking after it!)

If you’ve ever wondered what your immune system does and why it’s so important then this article should help shed some light.

The immune system basics

The main purpose of your immune system is to protect your body from viruses and bacteria. Without it, they’d have free reign and you’d be constantly falling ill.

Your immune system works by recognising the difference between your body’s cells and alien cells, allowing it to destroy any that could be potentially harmful.

This usually works well but can cause problems if your immune system wrongly classifies some of your own cells and attacks them instead.

Why exactly do you need a healthy immune system though?

A robust and properly functioning immune system helps you go about daily life as you come into contact with germs and bugs from pets, other people, and your environment.

Without a healthy immune system, you could pick up infections and infectious diseases more easily, and the effects could be serious – even fatal.

Your body’s first line of defence is its physical barriers. If viruses and bacteria manage to break through, there are specialised cells that will jump into action.

Your bloodstream and key areas of your body contain white blood cells that can fight and destroy the viruses and bacteria they find.

Sometimes, our immune system can overreact and even attack your body’s own cells. This is what happens in the case of allergies like hay fever and autoimmune diseases. It’s why donated blood and organs must be very careful matched.

It’s easy to take the immune system for granted because it does such a good job at keeping us free from infection around the clock! If you’ve got a healthy immune system, look after it and it will look after you.

Read more: How to support your immune system naturally

What makes up your immune system?

There are several components to the immune system. Some you will have heard of before but others are more obscure.

Here is a brief summary of the different parts and the important roles they play in keeping your body protected:


The skin is a physical barrier that keeps bacteria and germs at bay. Tears and saliva offer further protection as they’re anti-bacterial so can neutralise any invaders.


Anti-bacterial, sticky mucus lines your lungs and this catches germs and stops them from entering your bloodstream. Mucus is also found in your nasal passage and works in the same way.


Around seventy to eighty percent of your immune system cells are found in your gut. It’s often a place where bacteria and viruses attack so it’s important that your gut is in good condition and has plenty of friendly bacteria at its disposal.

Lymph system

Your lymph system carries water, food and oxygen to your cells and removes waste. It is made up of your bone marrow, spleen, thymus and lymph nodes.

In your bone marrow, your body’s disease-fighting white blood cells are produced and released. There are many different kinds of leukocytes (white blood cells) but they all produce anti-bodies to fight off specific bacteria and viruses. The main three types are granulocytes, lymphocytes (T-cells and B-cells) and monocytes.

Your spleen regulates how much blood is in your body and removes damaged cells. The thymus gland is where bacteria-fighting T-cells mature.  It’s located behind your breastbone and in the front part of your chest. It’s a vital part of a child’s immune system but is less important in adults. Lymph nodes are designed to detect any bacteria or infection in cell fluid and remove them. This can cause them to swell temporarily.

Five myths about the immune system

  1. Exercise makes no difference to your immune system

Not true. Regular exercise and living an active lifestyle can help keep your immune system healthy. Exercise gives your cardiovascular system a boost, which will help white blood cells circulate and support normal function of your lymphatic system.

While there’s no direct link between a workout and your immune system function, staying fit and active will help your immune system to help you.

  1. Everyone is born with the same healthy immune system

Unfortunately this isn’t true. If you have a healthy immune system, count yourself lucky (and look after it!). Some people are born with primary immunodeficiency disease.

This affects the body’s ability to defend itself against infection from bacteria, parasites, and viruses. There are more than 100 known congenital immunodeficiency disorders, including alymphocytosis, XLA (X-linked agammaglobulinemia) and CVID (common variable immunodeficiency).

  1. A healthy immune system can’t be damaged

Not true. If you are born with a healthy, normal immune system, episodes during your life can change it. In fact, acquired immune system disorders are more common that congenital ones. If an outside source (like an infection or a toxic chemical) attacks your body, it can cause lasting damage to your immune system.

Diabetes and malnutrition are among the list of things which can change a person’s immune system throughout life. So don’t take a healthy immune system for granted- do everything you can to protect it, so it can continue to protect you.

  1. Antibiotics help your immune system fight diseases

You’d think that antibiotics and your immune system are on the same team, right? While they both want to get you healthy, antibiotic use can actually weaken your immune system. Antibiotics don’t actually interact with the cells of the immune system, so they don’t directly affect it.

However, unnecessary antibiotic use stops your natural immune system from being challenged, causing it to slow down regulation and get weaker. The solution? Only take antibiotics when you absolutely have to, and take measures to build up your gut bacteria and immune system afterwards.

  1. Your immune system will stay the same throughout your life

This might surprise you, but your immune system ages just like you do. Your immune system gets older just like every cell and system in your body does.

Your body’s ability to fight infection gets weaker and this double-whammy can leave older people more prone to illness. Keep your immune system healthy as you get older by getting enough exercise, managing daily stress, and eating a healthy diet with plenty of fruit and vegetables.

How you can help your immune system

It’s vital that your immune system is in good working order if you want to stay as protected as possible. There are several ways you can support your immune system naturally.

You can cut down on the amount of alcohol you drink, start exercising regularly if you don’t already, and try to reduce your stress levels. If you live a hectic life, simply learning to slow down and rest occasionally can have a big impact.

Diet has an important part to play and if you can, you should try to eat some immune-boosting fruits and vegetables every day. You can take them in liquid form by making juices and smoothies if you’ll find this easier.

The advice in this article is for information only and should not replace medical care. Please check with your GP or healthcare professional before trying any supplements, treatments or remedies. Food supplements must not be used as a substitute for a varied and balanced diet and a healthy lifestyle.

Last updated: 13 July 2021


Author: Donia HilalNutritionist

Joined Holland & Barrett: Jan 2018

Bsc in Nutrition, Registered Associate Nutritionist and Certification in Pre and Post Natal Nutrition

Donia started her career as a freelance nutritionist, later she joined Nestle as their Market Nutritionist to help support their healthier product range, before joining the team at Holland & Barrett in January 2018.

Donia has over 6 years experience as a Nutritionist and also works with clients on a one to one basis to support their goals which include weight loss, prenatal and postnatal nutrition and children’s health.

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