Think about the last time you had a cold or suffered from allergies … stuffed or runny nose, watery or itchy eyes, maybe a sore throat. What about going through bouts of stress and noticing that your gut is acting up? These symptoms are all part of the plan (of keeping you safe and alive) according to your immune system—particularly the mucosal immune system.
What exactly is the mucosal immune system?
It almost sounds like a riddle: what provides the interface between you and the world but is not your skin? The answer is the mucosal tissue that lines the areas where your “inside” is exposed to the outside world, albeit through a system that contains epithelial cells and a layer of mucus. That’s the respiratory system (nose to lungs), digestive tract (mouth to colon), and urogenital organs, and it is where the meet-and-greet as well as the defend-and-annihilate happen.
These processes, much like most of the work of our immune system, happen without us being aware of them—except for when we get sick, have allergies or asthma, or suffer from gut-related issues or urinary tract infections.
About that mucus layer
Each mucosal surface in the body produces its own protective mucus layer—and far from being a passive coating, this mucus is a highly organized and active part of the immune system. It contains beneficial microbes, antimicrobial proteins, and immune molecules such as immunoglobulin A (IgA), all working together to help keep harmful invaders in check. Even the eyes have a delicate mucosal layer that keeps their surface lubricated while helping protect against dust, debris, and pathogens.
This “cocktail” is quite complex:
- helps beneficial bacteria stay in place
- blocks potentially harmful microbes
- protects the cells beneath the surface
- supports the immune cells that patrol these busy front-line tissues
Damage to the mucus layer means higher risk of inflammation, which can lead to chronic conditions, infections, and autoimmune diseases. That approximately 70 percent of our immune system resides in proximity to the gut is no mistake. Through our breathing, eating, and well … living, we encounter millions of microbes and viruses every single day, many of which have the potential to make us sick.
The immune cells in the nose and mouth mucosa must learn whether incoming microbes and molecules are safe or not. Babies explore the world with their mouths for a vital reason: their developing immune systems are learning which microbes and molecules are harmless and which may require a response.
Nasal sprays and immune defence
Nasal sprays can shift nasal care from simple symptom relief to supporting the immune system’s first line of defence. Always consult a medical professional before using nasal sprays.
- Sterile saline solution can be used to help flush out allergens, dust, and irritants and to maintain or restore the moist environment inside the nose, especially during a cold or allergy season.
- Steroid sprays (over the counter and by prescription) can relieve allergy symptoms, but they can have side effects and need to be properly administered.
- Antihistamine and decongestant sprays (available by prescription) can provide relief from a stuffy nose and for allergy-related itching and sneezing.
Strength is not about being loud
An overactive immune system is not the answer. Being hyperreactive can result in excessive inflammation, autoimmune conditions, severe allergies and asthma, and chemical sensitivities.
Immunity is less about “strength” and more about regulation, tolerance, and signalling. The mucosal tissues must distinguish between genuine threats and harmless exposures such as food, environmental particles, and beneficial resident microbes. That requires finely tuned signalling between cells, including immune cells, antibodies such as secretory IgA, and local chemical messengers.
A well-functioning immune system is the result of learning to distinguish between friend and foe and acting accordingly.
The gut, the microbiota, and immunity
Everyday habits play a major role in how well the mucosal immune system functions. Diet is one of the biggest influences: fibre-rich whole foods and fermented foods can help support a healthy immune response, while diets high in ultra-processed foods and low in fibre may do the opposite. Chronic stress can also take a toll, affecting the body’s ability to maintain a healthy immune balance.
In the large intestine—home to most of the gut microbiome—the immune system is constantly monitoring what passes through, from nutrients to potential pathogens. Here, immune cells work closely with gut microbes in a remarkably active partnership. As beneficial bacteria break down dietary fibre, they produce compounds that help nourish and maintain the protective mucus layer lining the gut. This thin barrier sits atop a single layer of cells that carefully separates the contents of the gut from the rest of the body.
That a tightly connected layer of cells, along with the mucus layer on top, provides an effective barrier that keeps us healthy is nothing short of amazing.
Understanding “leaky gut”
Intestinal permeability (often referred to as “leaky gut”) happens when certain pathogens and molecules that are usually contained in the gut “leak” through the gut barrier, potentially impacting skin and brain health.
The impact of stress on the immune function
Bouts of acute stress can manifest as “butterflies” in the tummy, bloating, pain, and/or motility issues (diarrhea or constipation).
Chronic stress, however, can alter the composition of the gut microbiota and the integrity of the gut barrier, which can result in “gaps” that allow for food molecules or bacteria to get through and wreak havoc inside the body. This can increase the risk of metabolic and bowel disease and autoimmune conditions.
Life stresses cannot be wished away, but good habits can help. Aim to sit down for your meals, take a few deep breaths before starting, and enjoy food slowly, for you and your future self.
Our well-being, including a robust immune system, is supported by healthy habits and a marvellous network of hard-working cells and microbes.
How to support the mucosal immune system
- Adequate sleep enables the production of new immune cells and allows for pathogen clearance to occur.
- A fibre-rich, plant-predominant diet provides different types of fibre that beneficial gut bacteria need to thrive. In return, these microbes produce short-chain fatty acids—such as acetate, butyrate, and propionate—that help nourish the gut lining, support a healthy gut barrier, and feed other beneficial bacteria.
- Prebiotic supplements can help when the diet lacks fibre or when certain gut conditions are present.
- Fermented foods provide beneficial bacteria, while probiotic supplements can be helpful, especially when gut-related issues are present.
- Bovine colostrum may help support gut health, particularly in athletes .
- Goldenseal may help modulate the inflammatory response, though it may also interact with certain medications or have side effects.
- Zinc helps support the immune system and may reduce cold duration. Zinc lozenges consumed within 24 hours of initial cold symptoms can help ease symptoms.
- Vitamin A aids in the development of white blood cells, which are essential to immune function. Liver, eggs, and dairy are great sources, while orange and yellow produce provide provitamin A, which is converted to vitamin A.
- N-acetylcysteine may help support mucosal tissues indirectly by influencing mucus quality and antioxidant defences.
This article was originally published in the September 2026 issue of alive magazine.