A Guide to The Immune System

Person with hand sanitiser and tissues to protect the immune system

In this brief guide to the immune system, we explain how it works, how it keeps you healthy, the consequences of having a weak immune system, and how you can boost your immune system to help prevent illness and stay healthy.

In this guide, we will cover the following:

  1. What is the immune system?
  2. How does the immune system fight off infections?
  3. What can cause weak immunity?
  4. Signs of a weak immune system
  5. What is an overactive immune system, and how can it affect you?
  6. Does age affect the immune system?
  7. How to boost your immune system
  8. Preventing illness

What is the immune system?

The immune system includes several different components – it is a complex system comprised of proteins and cells working together to fend off antigens (harmful substances).[i]

The immune system memorises antigens it has previously defeated. Therefore, if the antigen enters the body again the immune system recognises and destroys it quickly before the antigen can reproduce and cause illness.

  • White Blood Cells – Your immune system includes several types of white blood cells that work together to fend off infection. These include phagocytes (cells that surround and break down pathogens)[ii] and lymphocytes (which are triggered when they encounter antigens).[iii]
  • Antibodies – Antibodies are chemicals, cells, and proteins that work together to identify and mark toxins for destruction.
  • Complement system – As the name suggests, these proteins ‘complement’ the work of the antibodies.
  • Lymphatic system – As one of your body’s vital networks, the lymphatic system contains lymph nodes (which capture microbes), lymph vessels (which carries lymph, a fluid rich in white blood cells through the lymphatic system), and lymphocytes (a specific type of white blood cell that fights infections).[iv]
  • Lymphocytes – There are two main types of Lymphocytes, T cells and B cells. T cells can recognise viral antigens surrounding infected cells, while B cells can recognise antigens present on the surfaces of viruses and bacteria.[v]
  • Spleen – Your spleen filters blood to remove microbes and old or damaged red blood cells. The spleen also generates antibodies and lymphocytes.
  • Bone marrow – Found inside the bones, marrow produces red and white blood cells, and platelets (clotting agents).
  • Thymus – Your thymus filters your blood and produces T-lymphocytes.

How does the immune system fight off infections?

Humans are susceptible to two main types of infections: bacterial and viral. Your body’s immune system tackles these infections in slightly different ways.[vi]

  • Bacterial infections – Your body fights bacterial infections by increasing local blood flow to the area, which results in inflammation and swelling. The site is flooded with white blood cells to recognise, fight and destroy the bacteria. Antibodies are created, which attach to the bacteria and help destroy them.
  • Viral infections – Viruses hide within otherwise healthy cells, presenting quite a challenge to your immune system. However, as the virus multiplies the surface of the affected cells changes allowing the T-lymphocyte cells to recognise and destroy these infected cells. When the virus leaves the infected cell, it will be attacked by antibodies that have been produced as a response to infection or previous vaccination.

What can cause weak immunity?

Our immune system protects us against viruses, bacteria and other microorganisms. Sometimes our immune system (white blood cells) can become weakened. A weakened immune system can also be referred to as immunocompromised which can leave us more susceptible to illness. The immune system can be weakened by cancer, diabetes, HIV, lupus, certain medications and treatments such as corticosteroids, chemotherapy and radiotherapy.

Signs of a weak immune system

If you are concerned about your immune system, be sure to speak with your GP. Here are some of the most common signs of a weak immune system.[vii]

  • High stress levels Stress can inhibit your white blood cell production. Long term stress can therefore affect your body’s ability to fight off viruses and bacterial infections, making you more susceptible to being unwell.
  • Digestive problems If you suffer with faecal incontinence, digestive problems caused by a weaker immune system may exacerbate your symptoms. To effectively manage the increased symptoms, it may be necessary to review your current choice of incontinence product to ensure you have the best shape and fit for your needs. You should always contact your GP if incontinence symptoms increase or worsen.
  • You regularly catch colds
    It’s quite common to catch one or two colds every year. While they are inconvenient and irritating, most people generally recover in around a week. However, if you catch more than the average one or two colds a year, it could mean you have a lowered immune system, and it may take you longer to recover.
  • Your wounds don’t heal quickly
    After your skin is compromised, your body immediately starts working to protect the wound and create new skin. If you suffer from a lowered immune system, this process can take a lot longer than average.
  • You frequently experience infections
    If you experience more frequent episodes of infections such as ear infections, pneumonia, or sinusitis this could be your body’s way of telling you that your immune system is lowered.
  • You feel lethargic and tired
    If you are getting the right amount of sleep (6 to 9 hours per night) and you still feel exhausted, this could be a sign that your immune system is low.

What is an overactive immune system, and how can it affect you?

Having an overactive immune system comes with unique challenges. Some substances (known as allergens) that would usually be harmless, can for some people cause mild to severe allergic reactions.  Allergens such as mould, dust, pollen, and certain foods like fish and nuts can be triggers for an allergic reaction. The most severe reaction is known as anaphylaxis[viii]. Common conditions brought on by an overactive immune system include asthma, eczema, and allergic rhinitis.

Does age affect the immune system?

Sadly, our immune system is affected as we get older. As you age, your thymus and bone marrow produce fewer B and T cells, and the function of your mature lymphocytes diminishes.[ix] As a result, it takes longer to ‘bounce back’ from illnesses and wounds take longer to heal.

How to boost your immune system

Your immune system is a complex combination of different responses, processes, and systems within the body, working in harmony to keep you well and prevent illness. As a result, there is no one way to boost its efficacy.

That said, exercise, diet, sleep, hygiene and lifestyle factors are all proven ways to improve your overall health and wellbeing. By staying in good health, you can keep your body robust and strong, which are essential factors for throwing off illnesses.


Exercise reduces stress, improves sleep, and helps you maintain a healthy weight. These are all essential aspects of a healthy and functioning immune system.


Ensure that you get a varied diet rich in different nutrients, herbs, and vitamins.

  • Food – Your diet should include a wide array of fresh fruits and vegetables, along with whole grains, oily fish, and lean protein.
  • Vitamins – Some of the best vitamins for your immune system health include Vitamin C, which your body cannot produce or store, Vitamin B6 (to boost your immune system’s biochemical reactions), and Vitamin E, an antioxidant.[x]
  • Herbs – According to traditional Chinese medicine principles, certain herbs are antagonistic to pathogens and toxins. That means that they help you fend off bacteria, parasites, and viruses.[xi] These herbs include echinacea, garlic, ginseng, and reishi mushrooms. (Please note that your GP should always be consulted before taking any new over the counter medicines as it may interact with your prescribed medication)


Good quality sleep is essential for overall health [xii]. Whilst you sleep your immune systems releases proteins called cytokines. Some cytokine production increases if your body has an infection, inflammation or is stressed. Cytokines can also help promote sleep.


There are several lifestyle factors that can impact the immune system. For example, alcohol can impair the function of your immune cells.[xiii] If you want to improve your health and boost a low immune system, you should lower your alcohol consumption, quit smoking, and limit the amount of stress you experience. Try replacing your unhealthy habits with meditation, long walks, and relaxing hobbies that you enjoy.

Preventing illness

While science has not uncovered the secret to improving the immune system, there are plenty of measures you can take to prevent illness. Give your immune system a helping hand with the following:

  • Get vaccinated
    You can protect yourself by having the seasonal flu, COVID-19 and pneumonia vaccinations if you are eligible.
  • Keep surfaces clean
    Viruses can live on metal, plastic, fabric, glass, and paper. Help your immune system by regularly sanitising surfaces in your home and washing your hands frequently.
  • Natural ventilation
    Having a window open allows fresh air to circulate and improves ventilation. The current COVID-19 pandemic requires a face-covering to be worn in certain settings when social distancing is difficult to reduce the risk of transmission of the virus. Please refer to the government’s up to date guidance found at www.gov.uk.
  • Take vitamins
    Vitamins in vegetables, meat, nuts, and fish help keep your immune system functioning. If you have a vitamin deficiency, you are more likely to catch viruses and experience infections. The NHS website provides guidance on taking vitamins such as zinc, which may be prescribed by a GP if you are deficient.

Take charge of your immune system and wellness

No one wants to get sick. By eating well, exercising more, and lowering your stress levels, you can increase your quality of life and improve your immune system’s functionality.

Reference list

Better Health Channel (2012). Immune system. [online] Vic.gov.au. Available at: https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/immune-system [Accessed 18 Jan. 2021].

Better Health Channel (2014). Infections – bacterial and viral. [online] Vic.gov.au. Available at: https://www.betterhealth.vic.gov.au/health/ConditionsAndTreatments/infections-bacterial-and-viral [Accessed 18 Jan. 2021].

Cleveland Clinic (2016). 3 Vitamins That Are Best for Boosting Your Immunity. [online] Health Essentials from Cleveland Clinic. Available at: https://health.clevelandclinic.org/3-vitamins-best-boosting-immunity/ [Accessed 18 Jan. 2021].

February 2018, K.A.Z.-L.S.C. 21 (2018). Lymphatic System: Facts, Functions & Diseases. [online] livescience.com. Available at: https://www.livescience.com/26983-lymphatic-system.html#:~:text=The%20lymphatic%20system%20is%20a [Accessed 18 Jan. 2021].

Harvard Medical School (2020). How to boost your immune system. [online] Harvard Health. Available at: https://www.health.harvard.edu/staying-healthy/how-to-boost-your-immune-system#:~:text=Every%20part%20of%20your%20body [Accessed 18 Jan. 2021].

Hasan, N. (2020). 6 Signs You Have a Weakened Immune System – Penn Medicine. [online] Pennmedicine.org. Available at: https://www.pennmedicine.org/updates/blogs/health-and-wellness/2020/march/weakened-immune-system [Accessed 18 Jan. 2021].

Janeway, C.A., Travers, P., Walport, M. and Shlomchik, M.J. (2014). The components of the immune system. [online] Nih.gov. Available at: https://www.ncbi.nlm.nih.gov/books/NBK27092/ [Accessed 18 Jan. 2021].

Johns Hopkins Medicine (2018). Disorders of the Immune System. [online] www.hopkinsmedicine.org. Available at: https://www.hopkinsmedicine.org/health/conditions-and-diseases/disorders-of-the-immune-system#:~:text=An%20overactive%20immune%20system [Accessed 18 Jan. 2021].

Laderer, A. (2020). 4 herbs that may help boost your immune system naturally. [online] Insider. Available at: https://www.insider.com/herbs-to-boost-immune-system [Accessed 18 Jan. 2021].

Montecino-Rodriguez, E., Berent-Maoz, B. and Dorshkind, K. (2013). Causes, consequences, and reversal of immune system aging. Journal of Clinical Investigation, [online] 123(3), pp.958–965. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3582124/.

Newman, T. (2018). The immune system: Cells, tissues, function, and disease. [online] www.medicalnewstoday.com. Available at: https://www.medicalnewstoday.com/articles/320101#the-immune-response [Accessed 18 Jan. 2021].

Olson, E. (2018). Can lack of sleep make you sick? [online] Mayo Clinic. Available at: https://www.mayoclinic.org/diseases-conditions/insomnia/expert-answers/lack-of-sleep/faq-20057757#:~:text=During%20sleep%2C%20your%20immune%20system [Accessed 18 Jan. 2021].

O’Neill, M. (2020). What Is a Weak Immune System? Here’s How Doctors Explain It. [online] Health.com. Available at: https://www.health.com/condition/autoimmune-disease/weak-immune-system [Accessed 18 Jan. 2021].

Panawala, L. (2017). Difference Between T Cells and B Cells. [online] ResearchGate. Available at: https://www.researchgate.net/publication/320182585_Difference_Between_T_Cells_and_B_Cells#:~:text=pathogens%20by%20phagocytosis.- [Accessed 18 Jan. 2021].

Ries, J. (2020). How Alcohol Can Affect Your Immune System. [online] Healthline. Available at: https://www.healthline.com/health-news/can-alcohol-hurt-your-immune-system-during-covid-19-outbreak [Accessed 18 Jan. 2021].


[i] https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/immune-system
[ii] https://www.medicalnewstoday.com/articles/320101#the-immune-response
[iii] https://www.ncbi.nlm.nih.gov/books/NBK27092/
[iv] https://www.livescience.com/26983-lymphatic-system.html#:~:text=The%20lymphatic%20system%20is%20a,blood%20cells%2C%20throughout%20the%20body.
[vi] https://www.betterhealth.vic.gov.au/health/ConditionsAndTreatments/infections-bacterial-and-viral
[vii] https://www.pennmedicine.org/updates/blogs/health-and-wellness/2020/march/weakened-immune-system
[viii] https://www.hopkinsmedicine.org/health/conditions-and-diseases/disorders-of-the-immune-system#:~:text=An%20overactive%20immune%20system,of%20an%20overactive%20immune%20system.
[x] https://health.clevelandclinic.org/3-vitamins-best-boosting-immunity/
[xi] https://www.insider.com/herbs-to-boost-immune-system
[xii] https://www.mayoclinic.org/diseases-conditions/insomnia/expert-answers/lack-of-sleep/faq-20057757#:~:text=During%20sleep%2C%20your%20immune%20system,production%20of%20these%20protective%20cytokines.
[xiii] https://www.healthline.com/health-news/can-alcohol-hurt-your-immune-system-during-covid-19-outbreak

Previous Post
Everything You Need to Know About Sleep
Next Post
A Useful Guide to Blood Pressure

Related Posts

Leave a Reply

Your email address will not be published.

Fill out this field
Fill out this field
Please enter a valid email address.