Caught yet another cold? Here’s why you’re always getting sick in cold and flu season

It’s cold and flu season, and you’re sick again. You’re the person who always picks up whatever respiratory virus is making the rounds, and you always seem to take a while to get over each infection. Meanwhile, a fellow commuter has just coughed twice in your enclosed space without covering their mouth. You know what’s coming.

A robust immune system is integral to your overall health. It is fundamental to fighting off microbes or pathogens and produces potent fighters. But the immune system can be weakened, making us more susceptible to infections and slower to recover. This post will examine why you might struggle to escape the latest winter bugs.




How the Immune System Works


As humans, we’re attacked on a daily basis by a host of marauding invaders who look at our bodies as the place to reproduce and feed themselves. Our immune system is our body’s defence system, and any invader – virus, bacteria, fungi, toxins – that makes its way through our physical defence barrier (i.e. skin and epithelial linings) is met with a swift, local response. This first wave of our defence forces comprises several cells, proteins and organs like your spleen, thymus and lymph nodes. They all work together to fight off these invaders. The cells of the immune system include white blood cells, such as neutrophils, lymphocytes and macrophages, which travel around the body looking for invaders and signs of damage. These cells have an indiscriminate response and work in many different ways; some will engulf and eat the invader, while others use bleach-like substances to kill it.


If, after some time, these front-line forces, known as the innate immune system, haven’t managed to get the invasion under control, the second part of the immune system, the adaptive immune system, will kick into gear. The adaptive immune system is made up of B cells that produce antibodies to particular pathogens and T cells that directly attack infected or cancerous cells, encourage other white blood cells to destroy the pathogens and stimulate B cells to produce antibodies. This part of the system is more discerning, and that’s because, throughout your lifetime, it builds up a memory of all its previous encounters with foreign invaders. Consequently, it can remember when they show up and uses specific tools, like antibodies, to target the invader whenever it makes an appearance.


But as with all battles, collateral damage can occur. So, the immune system has a repair function that helps resolve any damage due to the invader and/or the body’s response.

What Weakens the Immune System?


At the time of writing, our What’s Your Body Trying to Tell You quiz  has been taken by more than seven thousand people, and more than half of quiz completer’s symptoms appear to correlate with immune function concerns. A result like that may seem unusual, but it is likely because the immune system is intricate, with lots of moving parts, making it highly susceptible to things going wrong. And when things go wrong, they can have devastating effects. 


Sometimes, while out on patrol, the white blood cells may get a little overzealous and launch attacks on relatively innocuous substances like pollen, animal hair or dust, causing an allergic response that leads to conditions and symptoms of hayfever, asthma and eczema. The ubiquitous nature of these substances in our environment can lead to our immune response being constantly activated and running at a low level, causing inflammation and damage to the body. On other occasions, the programming of white blood cells goes haywire, causing these cells to go rogue and attack healthy body cells, as in autoimmune diseases like type 1 diabetes, Rheumatoid arthritis, Crohn’s disease and Hashimoto’s thyroiditis. 


At the other end of the spectrum, the immune system may not be as reactive as it should be, leaving the human susceptible to infection. This can happen due to genetic factors that mean some people are born without some of the body’s immune system or with it not working properly. This is known as primary immunodeficiency, and there are more than 300 forms of this disorder varying from mild to severe, and treatments are used to help support the immune system. People can also develop a compromised immune system as a result of certain chronic diseases and the use of immunosuppressant drugs, certain cancers, as well as the human immunodeficiency virus (HIV) and the development of acquired immune deficiency syndrome (AIDS). 


Our immune system also declines as we age, and we become less good at producing white blood cells. But, environmental, nutritional and lifestyle factors also play a role beyond unmodifiable factors like age and genetics that weaken the immune system.


Chemical Exposures


You’ve probably heard that ~70% of all immune cells call the gut home and that our digestive system is home to trillions of bacteria collectively making up the gut microbiome. Many harmful chemical exposures can interfere with the health of our gut, affecting the microbiome and the integrity of the gut lining. Our microbiome plays a role in training and regulating our immune system. There is a lot of research going back decades, looking at the impact of environmental toxins on immune health. The evidence suggests that exposure can lead to weakened immune systems or hyperactivity of the immune response. 


Endocrine-disrupting chemicals are, according to the National Institutes of Health (NIH), “Chemicals that may interfere with the body’s endocrine [hormonal] system and produce adverse developmental, reproductive, neurological, and immune effects in both humans and wildlife.” These chemicals, including bisphenols such as BPA and the BPA replacements BPS and BPF, suppress the immune system, weakening its response to infectious diseases. Environmental chemicals like per- and polyfluoroalkyl substances (PFAS) are another class of chemicals, much like bisphenols, which are highly persistent, so much so that most people are estimated to have PFAS compounds in their bodies. Exposure to these chemicals suppresses the immune system’s antibody response and increases allergic symptoms.



As we’ve seen above, the immune system will be affected when the gut microbiome is compromised. Anything that disrupts the gut microbiome, particularly encouraging the growth of more harmful bacteria and fewer beneficial bacteria to counteract this growth, can cause dysbiosis. Dysbiosis will contribute to unresolved inflammation, affecting innate immunity and, therefore, our ability to respond to invasions by invaders. It also changes the overall immune system balance, potentially increasing the likelihood of allergic and autoimmune conditions.


Processed Foods


Processed foods, particularly ultra-processed foods, with their emulsifiers, sweeteners and ingredients devoid of nutritional value, thin the mucus lining in the gut and disrupt the microbiome, leading to dysbiosis and other digestive issues. Dysbiosis, as we’ve seen above, can lead to inflammation in the gut lining and can increase the permeability of the gut lining, commonly referred to as “leaky gut”. As the name implies, a “leaky gut” happens when the tight cell junctions between the epithelial cells of the gut lining loosen, allowing molecules and partially digested proteins from the digestive tract to seep into the bloodstream. The immune system will view these substances as foreign as they should not be in the blood, where they will drive inflammation, perpetuate immune activation and promote immune imbalance. This explains why there is so much emphasis on supporting and maintaining good gut health when working to improve immune health. 



Blood Sugar Imbalances


An inability to maintain stable, steady blood sugar or, more accurately, glucose levels will drive inflammation and negatively impact immune function. Foods with a high glycaemic load will cause blood glucose levels to fluctuate wildly, leading to steep rises in blood glucose levels. High blood glucose levels will also negatively impact the body’s antioxidant system. This system helps reduce the damage caused by free radicals – reactive oxygen species that damage DNA and increase the likelihood of premature ageing. When there is an imbalance between the free radicals in the body and the body’s antioxidant capacity, oxidative stress occurs, which damages proteins and DNA and triggers disease.


Underlying Health Conditions


Several health conditions can also impact immune function:




Hyperglycaemia or chronically high blood glucose levels, as experienced in poorly controlled diabetes (type 1 or type 2), can affect the immune system by damaging the proper function of white blood cells and reducing the body’s ability to fight off foreign invaders like toxins, bacteria and viruses. High blood glucose also reduces blood flow, making the blood thick and reducing its ability to travel through smaller networks of blood vessels, particularly in the kidneys, eyes, heart, feet and nerves. This is why people with type 2 diabetes are encouraged to attend their checks regularly. The reduced blood flow also prevents the body from being able to mount a normal immune response. 


Cardiovascular Diseases


These conditions affect the heart, its muscles, blood vessels, valves and the heart’s rhythm and can include genetic conditions. You’ve probably heard of atherosclerosis, which happens when the blood vessels become narrowed or blocked, preventing blood from flowing freely and leading to a risk of heart attacks or strokes. Much like diabetes, this reduced blood flow prevents the proper transport of immune-supportive nutrients and the removal of toxins and waste, which damage the body.


In addition, the immune system will also view the build-up of atherosclerotic cholesterol plaques inside the heart’s blood vessels as a foreign invader and will activate immune processes to remove it. This, in turn, drives inflammation, and the prolonged state of inflammation causes damage and means that the immune system resources are diverted, making it easier for infections to take hold.  



Lung Diseases


Conditions like asthma, chronic obstructive pulmonary disease, and chronic pneumonia result from irritation of the lungs and airways, which drives inflammation and makes breathing difficult. The unchecked inflammation common with these conditions will cause the immune system to continue to mount a response, leading to chronically inflamed lungs. Inevitably, this causes extensive damage and impairs the immune response to respiratory infections.


Stress + Sleep


Lifestyle factors like stress and sleep can also impact proper immune function. As you’ve probably experienced during stressful events, stress will change health behaviours, especially around food. It makes you much more likely to consume foods that harm your gut microbiome and elevate blood glucose. Stress also causes a hormonal cascade that further elevates blood glucose and dampens the immune system. 


Stress and sleep will also negatively impact each other and cause a vicious cycle. Stress hormones affect your sleep quality and reduce your immune system’s ability to be strengthened as you sleep. Which further stresses the body and impacts your sleep. Chronic sleep deprivation, on the other hand, will also drive the stress response.


All of these factors impact your immune system by reducing your innate immune response and increasing your vulnerability to infection.

Signs of a Weakened Immune System


So, your immune system might not be firing on all cylinders. How do you know? Well, there are some tell-tale signs to look for:


You catch everything going, and it takes a long while for you to recover.

If you’re prone to catching whatever is going around or need to take antibiotics on multiple occasions over the year to assist your body in fighting infections, it could be a sign that your body’s defences aren’t as strong as they could be. Moreover, the length of time it takes to get over infections and the length of time you remain infection-free are also good indicators of the strength of your immune system.


Experience Digestive Issues

The close association of the immune and digestive systems can explain why regularly experiencing digestive distress could indicate poor immune function. These digestive issues include food sensitivities, abdominal pain and bloating. All of which could lead to increased intestinal permeability or dysbiosis.


Skin Breakouts and Rashes are Common

The skin is your largest organ and a significant component of the immune system, providing a protective barrier function that allows your body to get rid of things through sweating while preventing the entry of bacteria that could harm you. Unexplained acne, dermatitis, eczema and unusual rashes result from inflammation, which, as we’ve seen, can be a feature of impaired immune function.


Tiredness and Fatigue are Common

Tiredness and fatigue can be caused by many factors, including blood sugar problems [Link to Previous blog post], poor sleep and stress. Inadequate sleep and stress management practices will also drive blood sugar problems. In addition, fighting off infections and activating the immune response is an energetically expensive process, and if that’s happening frequently, you’re more likely to experience tiredness and fatigue.

The Upshot

As we’ve explored, various factors can weaken your immune system, from genetics and chronic diseases to lifestyle and environmental influences; it’s clear that maintaining robust immunity is a complex but crucial aspect of your overall health.


If you’re experiencing frequent illnesses, digestive issues, skin problems, or persistent fatigue, these might be signs that your immune system needs attention. Remember, you’re not alone on this journey. The Thrive Practice is dedicated to helping you understand and strengthen your immune health with personalised, holistic strategies. Whether it’s adjusting your diet, addressing stress, or managing underlying health conditions, we’re here to support you every step of the way. Don’t let a weakened immune system hold you back. Contact us today, and let us guide and equip you with the right tools and knowledge to recover quickly, stay healthy and increase resilience.


Hello, I’m Leah! Functional health consultant and founder of The Thrive Practice. Driven by data and supported by science, I’m unerringly obsessed with exploring your unique biochemistry to methodically get to the root of your health issues. So, you can achieve real and lasting relief.


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