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Your guide to low immune systems

14 Sep 2021 • 6 min read


Your immune system protects you from illness and infection.

It is a complex network of cells and organs – including your skin and white blood cells – which work together as a first and second line of defence.

Some parts of your immune system (including your skin and mucus membranes) try hard to keep infection out.

But if a virus, parasite, or bacteria makes its way into your body, your immune system will fight back.

Why do some people have a low or no immune systems?

Immune systems are complex and vary from person to person.

If you have a strong immune system then your body will be able to fight off most illnesses whereas if you have a weak immune system, it won’t.

Why your immune system could be weak

You could be born with an inefficient immune system, or it could be weakened during your life.

If you are diagnosed with a poor immune system, the medical name is immunodeficiency disorder.

Remember how many parts of your body make up the immune system and how complex it is?

That’s why the term “immunodeficiency disorders” covers a number of symptoms, causes and health risks.

Which organs are part of your immune system?

Your immune system is a vast and complex system of cells, organs, and tissues. They work in harmony to detect and destroy any foreign germs which threaten your health.

The main organs of your immune system are the lymphoid organs, which house the important white blood cells which help get rid of infection.

These lymphoid organs include your lymph nodes, thymus, bone marrow, spleen, liver, adenoids and tonsils, and your skin.

A closer look at your lymphatic system

Your bone marrow is the tissue in the middle of your bones.

It is where white blood cells (called leukocytes) are produced and stored until they are needed to detect and destroy viruses or bacteria.

Your lymph nodes are little organs that also produce and store special cells that can fight infections.

Your thymus is an organ located between your lungs, which has an important role in your immune health.

This is where your T-cells live, which help destroy infected cells.

Did you know that your thymus grows until puberty and then starts to shrink as you age?

Your spleen is the largest organ in your lymphatic system. It is on the left-hand side of your abdomen, next to your stomach, and is about the size of a fist.

This is where your body stores more white blood cells that can fight off infection and illness.

How your immune response leaps into action

Your immune system has three main layers of defence. You probably don’t notice some of this happening, even though your body is working hard every day to protect you:1

  1. Firstly, your body maintains a healthy and safe barrier that aims to stop germs entering your body. This barrier includes your skin and mucus membranes.
  2. Secondly, your immune system will identify germs, viruses, and bacteria and try to destroy before it can start to reproduce in your body.
  3. Last but not least, if necessary your immune system will work hard to eliminate and get rid of a virus or bacteria which has started to make you sick.

The front line  

The front line of your immune system does its best to stop foreign invaders from getting into your body in the first place.

However, if a virus, bacteria, or parasite still makes its way through, the rest of your immune system will get to work.

The “army” of our immune system is made up of different types of white blood cells, all called defender cells.

We make about a billion of these defender cells in our bone marrow every day.2

What do the white blood cells do?

Some of these white blood cells – called macrophages – circulate around our body looking for germs and infection.

As soon as they see something they don’t recognise, they attack.

Your macrophages can tell the difference between your own cells and invading cells because of antigens.

Antigens are like ID-tags on the surface of every cell. If a new cell doesn’t carry your unique antigen, then your immune system knows it’s foreign and sees it as a threat.3

Did you know that macrophage literally means “big eater”, which is exactly what your macrophage white blood cells do to invading cells?

What’s the difference between a virus and a bacteria?

Your immune system will respond differently to a viral attack and a bacterial infection.

Compared to your own body’s cells, bacteria are small and simple.

While your body’s cells have a complex structure, including a nucleus, bacteria are just single-cells and around 1/100th the size of a human cell.4

What makes bacteria so dangerous is that they are independent – they can eat and reproduce very quickly under the right conditions.

In contrast, a virus isn’t alive like a bacteria is.

Think of a virus like a little bit of DNA that attaches itself to a cell and puts its own DNA into that cell. It uses the ability of a living cell to reproduce more virus particles.

What happens when the infection fights back?

Sometimes, the virus or bacteria will fight back against the macrophages.

This is when the next set of white blood cells comes into action in the form of the more powerful T- and B- lymphocyte cells.

Your B-cells make special proteins called antibodies which bind to the virus and stop it from replicating and getting any bigger.

They also tag the virus with a special message so other white blood cells can come and destroy them.

Your T-cells help the B-cells out in different ways. Some of them will put out a kind of alarm call within your body, rallying the troops of other white blood cells.

Others will destroy cells which have already been infected by the incoming virus, while some will help the B-cells to produce those important antibodies.5

What can impact your immune systems?

As you age, your immune system can become less effective. There are several other factors that can also cause this. These include:

  • Being stressed
  • Not sleeping well
  • Pushing your body too hard (or not enough)
  • Having an immunodeficiency disorder (such as leukaemia or AIDS)
  • Not eating healthily and failing to give your body the nutrients it needs
  • Smoking
  • Drinking alcohol
  • Having radiation therapy
  • Being exposed to harmful chemicals
  • Having multiple sclerosis, cancer, Crohn’s disease, Chronic Fatigue Syndrome or another condition that puts pressure on your immune system.

Weak immune system symptoms

There are certain tell-tale signs that can indicate if you have a weak immune system. We’ve listed five of them below:

  1. You’ve constantly got a cold

Having the old cold every now and then is normal, but if you’ve permanently got one, then your body could be telling you that your immune system’s really suffering.

Permanent colds are an indicator that your body isn’t equipped to fight off germs.

Catching two to three colds during the winter, that linger for a while, is a sure sign your immune system isn’t quite right.6

Handpicked content: How long does a cold last?

  1. You develop regular ear infections

By this, we mean more than four infections a year.

As with colds, if you’re constantly getting ear infections, then your body’s immune system isn’t quite firing on all cylinders.

It could possibly mean you have an underlying health condition.7

  1. You’re always tired

Most people feel tired as a result of the busy, always-switched-on lives we now all lead, but if you’re feeling permanently drained, then your immune system may not be operating properly.

This means you can get worn out quicker because your body’s having to work so hard to fit off germs, infections and bacteria.8

Handpicked content: How to fight fatigue

  1. You’re feeling really stressed

According to research, long-term stress is capable of weakening the immune system due to the fact it reduces our lymphocytes, the white blood cells that fight off infection.

The lower your white blood cell levels, the more likely you are to catch a cold or other form of infection.9

Handpicked content: How to tackle stress

  1. You’ve got digestive issues

If you experience diarrhoea for two to four weeks, then your immune system may not be functioning properly and may actually be harming the lining of your small intestine or digestive tract.

Constipation is also an alarm bell too.

If your bowel movements are hard to pass or look like small pellets, your immune system may be forcing your intestine to slow down.

This may also be being caused by bacteria, viruses and other health conditions too.10

Handpicked content: Digestion - The only overview you need

Immunodeficiency disorders

Whether you are born with an immunodeficiency disorder, inherit a genetic immune problem, or develop one, it will affect how your body can protect itself.

Any immunodeficiency disorder weakens your body’s in-built ability to identify and fight off infection.

There are two kinds of immunodeficiency disorders.

  1. Primary immunodeficiency disorder

If a baby is born with a weakened immune system, this is called primary immunodeficiency disorder. Scientists currently know of more than 100 primary immunodeficiency disorders.11

  1. Acquired immunodeficiency disorder

However if the immune system gets damaged or weakened later in life, it’s called acquired (or secondary) immunodeficiency disorder.12

Anything that damages the immune system can lead to acquired immunodeficiency disorder.

Acquired immunodeficiency disorders – the kind you can develop during your life – are more common than the type some babies are born with.

What a poor immune system could mean for your health

We already know that the immune system has an important role in keeping us healthy.

It identifies viruses, bacteria, and parasites and tries to stop them from entering our body.

If the infection does manage to get through the immune system’s first line of defence, then other parts of the immune system fight to get rid of the illness and help you feel better faster.

Your immune system releases white blood cells (called B cells and T cells) to fight off invading antigens and destroy foreign cells.

These unwanted invaders include viruses, bacteria, parasites, and cancer cells.

Any immunodeficiency disorder will affect how your body can protect you from infection and fight against disease.

If you have a poor immune system, you will catch viral and bacterial infections more easily than someone with a healthy immune system.

This could affect your life in a number of ways, from the annoyance and inconvenience of regular colds and hay fever, to the serious health risks of some cancers.

Some of the more serious health risks of a weak immune system include HIV and AIDS, viral hepatitis, cancers of the immune system (like leukaemia), or cancer of the plasma cells (called multiple myeloma).

Are you at risk of a weakened immune system?

We should all keep a close eye on our immune system health and support it by living a healthy and active lifestyle.

Some people might be at greater risk of a damaged immune system.

If you have a family history of primary immunodeficiency disorders, then your risk of having a primary disorder (or passing one on to your children) is higher.

Anything that threatens your immune system could potentially lead to secondary immunodeficiency disorder.

Exposure to infection, especially through bodily fluids, is a big risk factor, and cancer drugs and chemotherapy can put your immunity at risk too.

Our immune system can get weaker as we age, so it’s really important to stay healthy as you get older.

Get plenty of good quality sleep, minimise stress, eat a diet high in fruit, vegetables, protein, and fibre, and stay fit and active.


  • Your immune system is a complex network of cells and organs which work together as a first and second line of defence
  • Immune systems may vary from person to person
  • Factors that can weaken an immune system include stress, lack of sleep, an immunodeficiency disorder, illness and a poor diet
  • Symptoms of a weakened immune system include colds, ear infections, feeling tired or stressed and having digestive issues

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Which parts of your immune system can get damaged?

Here are just are some parts of your immune system which could be damaged or weakened during your life:

  • your skin
  • your bone marrow
  • your white blood cells
  • your spleen
  • your tonsils
  • your lymph nodes
  • your endocrine system (hormones)

It might be scary to think about having a weak immune system, but it’s an important topic to tackle.

If you think your lifestyle, fitness, or nutrition put you at risk of secondary immunodeficiency disorder, start taking steps now to live a healthier lifestyle.

The great news is that there is plenty you can do to give your immune system a helping hand.

Types of autoimmune disorder

There are over eighty different autoimmune disorders but here are some of the most common:13

Multiple sclerosis 

This is a condition that sees your immune system attacking the myelin that protects your nerve fibres, resulting in your nervous system not working as it should.

This can leave you with balance and vision problems, stiffness in your joints and spasms.14

Type 1 diabetes 

10% of people with diabetes have type 1.

Your body’s insulin-producing cells no longer work so glucose builds up in your bloodstream. To correct this, you have to take daily insulin injections.15

Handpicked content: Keeping your blood sugars balanced with food

Rheumatoid arthritis

This condition results in swelling, pain and stiffness in your joints and is the second most common form of arthritis in the UK.16

The joints usually affected include the hands, wrists, knees, feet and elbows.

Handpicked content: Natural ways to support arthritis

Coeliac disease 

More than 1 in 100 people have this condition and are unable to eat anything containing gluten.

If you have coeliac disease your body mistakes gluten as being harmful and will attack, causing damage to your intestines.17


Your melanocyte cells are responsible for producing melanin which gives your skin its colour.

When your body mistakenly attacks and destroys your melanocyte you’re left with white patches of skin.18

They can appear anywhere but are most common on your face, hands and other areas of exposed skin.


If you have psoriasis, your immune system causes your skin cells to be replaced every three to seven days, rather than every three to four weeks.19

This can leave your skin feeling sore, red and crusty.

Crohn’s disease

With this condition, your digestive system and/or gut doesn’t work as it should and becomes inflamed. It’s a form of Inflammatory Bowel Disease (IBD).20


Lupus is a serious immune system disorder that can affect the lungs, kidneys, blood cells, and nerves.21

There are lots of other less common health issues connected to a weak immune system.

These include Guillain-Bare syndrome, Graves’s disease, and Hashimoto’s thyroiditis.

Getting help with autoimmune disorders

There is currently no cure for autoimmune disorders but your doctor will be able to recommend various treatments that might elevate your symptoms once you’ve been diagnosed.

There is medication available for some types of autoimmune disorders but the problem is that they often don’t target a specific area so could reduce the effectiveness of your whole immune system.

It might be that making small changes to your diet and exercising more could help, or you may need to consider physiotherapy, acupuncture or hormone replacement therapy instead.

Your doctor will be happy to talk you through the different options available.

6 everyday actions that may be hurting your immune system

Washing your hands and sneezing into a hankie are obvious ways to protect your immune system.

But did you know though that there are lots of things you do every single day which could be damaging your immunity? 

  1. Not looking on the bright side

Your response to negative situations can affect your immune system.

If you tend to look for the risks and worries in a situation, try thinking like an optimist.

Pessimists are more stressed which can impact aspects of your immune system. What can you be grateful and happy about today?

Handpicked content: Simple strategies for keeping a positive mindset

  1. Keeping emotions bottled up

People who keep negative emotions to themselves tend to be sicker, more often.

This is because bottling up emotion can cause surges in blood pressure, white blood cells, and heart rate.

Share your problems, voice your frustrations, and learn how to air your differences with loved ones.

  1. Piling on the stress

Some stresses are worse for our immune system than others.

Everyday stress – called chronic stress – is bad for your health.

If you are constantly worried about finances, work, relationships, and other daily pressures, it’s time to look after your health.

Chronic stress impacts your immune system and ability to recover from illness. It’s time to find ways to relieve stress in a healthy way. 

Handpicked content: Comprehensive guide to stress

  1. Avoiding outdoor exercise

Busy days and dark evenings can mean it’s hard to get outside for exercise.

But it’s an important part of keeping your immune system healthy as exercise and activity keep white blood cells moving around your circulatory system.

Getting outside for any kind of activity will also expose you to local bugs, germs, and irritants, making your system more robust. You’ll be feeling happier, healthier, and fitter. 

Handpicked articleGet set to exercise in the cold

  1. Taking life too seriously

Parenting, running a household, studying, and progressing in your career are all serious things but you don’t have to take everything so seriously.

Lighten up a little and do your immune system a favour.

Laughing and smiling decrease damaging stress hormones which in turn helps give your immune system a boost. Do something that really makes you laugh every day – and share it with a friend if you can.

Handpicked content: Laughter yoga - Could laughter actually be the best form of therapy?

  1. Not getting enough sleep

Poor quality sleep (or not enough sleep) has a huge effect on immune system health.

There’s only so long you can burn the candle at both ends.

Lack of sleep is linked to lower immune system function and fewer germ-fighting cells in the body.

Make sure your bedroom is set up to invite 7-8 hours’ sleep, wind down before bed, and resist the urge to take your phone or tablet computer with you. It’s time to sleep.

Handpicked contentGuide to sleeping better – 34 natural sleeping remedies


  • Parts of your body that can be damaged by a weakened immune system include your skin, bone marrow, white blood cells, spleen, tonsils, lymph nodes and endocrine system
  • Autoimmune diseases include MS, type 1 diabetes, rheumatoid arthritis, Lupus and coeliac disease
  • Actions that can damage your immune system include insufficient sleep, being stressed, having a negative outlook and not taking enough exercise

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How you can help your immune system

If you feel you have a weakened immune system and can identify what might be causing it, you may be able to give your immune system a boost by making a few small changes.

Overall wellbeing

Stress has been linked to causing immune system disruption, so where possible, try to reduce your stress levels.

You can do this by:22

  • Getting a good night’s sleep
  • Not drinking too much alcohol or caffeine
  • Chatting through your worries with people you trust or writing them down
  • Relaxing by using mindfulness, meditation or breathing exercises
  • Doing more of what you love/enjoy doing most


Ideally, you want to be getting your ‘five a day’, as recommended by the NHS.

You may also want to go one step further by making sure your diet incorporates some, or all, of the vitamin and minerals, that are associated with good immune system health.

They include:23

  • Vitamin A – is found in liver, milk and cheese and dark green leafy vegetables and orange fruit
  • Vitamin C – is present in fruit and vegetables, including peppers, kiwis, oranges, tomatoes, blackcurrants and broccoli
  • Zinc – eat meat, poultry, eggs, cheese, as well as root veg, nuts and seeds, and wholegrain cereals and breads.
  • Selenium – is found in nuts and seeds, grains, vegetables, eggs, poultry, fish and shellfish
  • Vitamin D – mostly comes from sunshine, but is also found in oily fish, eggs, fortified breakfast cereals, spreads and dairy products

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Other measures to support your immunity

Other measures include: not smoking, exercising regularly to get more of those ‘feel good’ endorphins pumping around your body, maintaining a healthy weight and trying to avoid infection by washing your hands regularly and cooking meat thoroughly.24

Hopefully, your body will show/tell you if your immune system isn’t as strong as it should be by demonstrating symptoms like those listed above.

It’s also possible to take a blood test to determine if your body has the correct level of infection-fighting proteins (immunoglobulin) in your blood.

The test can also measure blood cell and immune system cell levels. Abnormal numbers of certain cells can indicate an immune system defect.

For more advice on this, speak to a medical professional.

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: 15 September 2021



Author: Bhupesh PanchalSenior Regulatory Affairs Associate

Joined Holland & Barrett: Apr 2019

Masters Degree in Toxicology and BSc Hons in Medical Biochemistry

Bhupesh started his career as a Clinical Toxicologist for Public Health England, advising healthcare professionals all around the country on how to manage clinical cases of adverse exposure to supplements, pharmaceuticals, cosmetics, industrial chemicals and agricultural products.

After 7 years in this role and a further year working as a drug safety officer in the pharmaceutical industry, Bhupesh joined Holland & Barrett as a Senior Regulatory Affairs Associate in 2019.

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