Seasonal change means different things to many people. For some, it’s great weather. For others it means itchy eyes, sneezing, and a stuffy nose. Misery, basically.
That’s hay fever. It’s characterised by endless sneezing and coughing. Earlier, this was considered an overreaction by the immune system to pollen. However, recent research has something else to say.
According to recent research, the answer to alleviating the hay fever systems are found in an unexpected place. It lies in the balance of bacteria residing in our gut and nose. “The gut-nose axis, a term used to describe the communication between these two microbial communities, highlights the interconnectedness of our body's systems,” explains Dubai-based Toni Zink, the medical director of Nabta Health clinic.
“When the gut microbiome is diverse and flourishing, it promotes a balanced immune response. However, disruptions in the gut-nose axis can lead to an exaggerated immune response, triggering the symptoms associated with hay fever,” she adds.
How so?
The gut and nasal microbiome
Before you reach for that industrial-sized doze of antihistamine to stop your uncontrollable sneezing, watery eyes, congestion and runny nose, you might want to re-evaluate your diet.
Our body is home to trillions of microorganisms, known as the microbiome, explains Zink. “This plays a role in various physiological processes. The gut microbiome in particular, has gained attention for its impact on the immune system. Recently, research has shown that a diverse and balanced gut microbiome is associated with a healthier immune response. This regulates inflammation and allergic reactions,” she explains. "A diversity of healthy gut microbiome and a substantial amount of good microorganisms in the nasal and oropharyngeal passages help make the immune system to become more discerning and be composed during environmental attacks," says Marian Alonzo, a medical expert from The Farm, in Philippines.
The right diet is key to the functioning of your immune system, as it consists of fibers, fermented foods like yoghurt or kimchi. This helps promote the growth of beneficial gut bacteria like Bifidobacteria and Lactobacilli genus.
When the gut microbiome is diverse and flourishing, it promotes a balanced immune response. However, disruptions in the gut-nose axis can lead to an exaggerated immune response, triggering the symptoms associated with hay fever ...
However, interestingly, this connection goes beyond the gut, reaching into the nasal passages. “The nasal microbiome, a community of bacteria residing in the nose, has been found to interact with the immune system and influence how the body responds to allergens like pollen. When this delicate balance is disrupted, as seen in an imbalanced microbiome, it can contribute to the development or exacerbation of hay fever symptoms,” she says.
‘A healthy gut means a healthy immune system’
“An essential part of our immune system's defense mechanism is our digestive system,” says Khalid Shukri, a Dubai-based physician at Wellth. Just like our respiratory system, it serves as an immunological barrier. It wards off foreign invaders, including germs, virus and allergies. And so, your gut health plays an essential role in controlling the immune system. “A healthy gut correlates with a healthy immune system, particularly when it comes to allergies,” he says.
An essential part of our immune system's defense mechanism is our digestive system. Just like our respiratory system, it serves as an immunological barrier. It wards off foreign invaders, including germs, virus and allergies. And so, your gut health plays an essential role in controlling the immune system.
The gut microbiome produces short-chain fatty acids. These are produced by gut bacteria during the fermentation of dietary fibre. “The food we eat alters the diversity and composition of bacteria in our gut. Sugary, processed foods, and 'bad' saturated fats have been linked to increased gut inflammation and decreased immunoglobulins,” Shukri explains. Immunoglobulins, also known as antibodies, are produced by white blood cells. It is a Y-shaped protein used by the immune system to identify and neutralise invaders such as unfriendly bacteria and viruses.
High sugar intake can also lead to the growth of harmful gut bacteria, while refined carbohydrates can cause blood sugar spikes, potentially affecting gut health. Artificial sweeteners also disrupt the balance of bacteria, along with frequent consumption of red meat.
What happens when there’s an imbalance in the gut microbiome
However, when there are lower levels of the strain of bacteria responsible for the production of short-chain fatty acids, there is a risk of hay fever. The Bifidobacterium genus and Lactobacillus genus are the two strains of bacteria responsible for producing these short-chain fatty acids. These are termed as the “friendly” bacteria, explains Shukri.
The Lactobacillus genus, includes L. acidophilus, L. rhamnosus, L. casei and L. plantarum. The acidophilus is found naturally in your mouth, gut, stomach, lungs, and urinary tract, and it can help restore balance in all of these microbiomes.
Research has shown that people with hay fever often exhibit differences in their gut and nasal microbiomes compared to those without the condition, explains Zink. People with hay fever have a less diverse gut microbiome. The reduced diversity of gut bacteria results in imbalance in the microbiome, and result in higher levels of inflammation, which is the body’s response to irritants, such as allergens, she says.
What happens when there’s an imbalance in the nasal microbiome
The community microorganisms living in our nasal passages are responsible for regulating the immune system and preventing pathogens from entering our body. The nasal passage has diverse microbes and is also the first point of contact, when it is exposed to the external environment.
So you can imagine the havoc, when these strains of bacteria get deeply affected. When there’s a reduced diversity of the nasal microbiome, there is a risk of respiratory infections.
According to research published in the 2014 article Seasonal Allergic Rhinitis Affects Sinonasal Microbiota, published in the American Journal of Rhinology and Allergy, some people have a different composition in terms of their nasal microbiome. They have more of a certain bacteria such as Staphylococcus aureus, which contributes to airway inflammation and a higher risk of hay fever symptoms.
Can probiotics and prebiotics help in reducing hay fever symptoms?
Well, research certainly seems to point in that direction. Probiotics are live microorganisms that are considered good for you. You’ll find them in yoghurt, cheeses like cheddar, mozzarella, cottage cheese, sauerkraut, pickles, buttermilk, kimchi and other fermented foods, according to the experts.
As many allergies correspond to imbalances in the microbiome, scientists believe that by restoring or increasing the diversity of bacteria in the gut, this will benefit the immune system. It will reduce the havoc created by hay fever. And so, there have been many studies regarding probiotics and how they can lower common inflammatory biomarkers such as C-reactive protein (CRP) and Interleukin 6 (IL-6), which are cells related to immune response that are associated with hay fever.
What research says
In 2017, author Jennifer Dennis, of the Department of Food Science and Human Nutrition at the University of Florida, USA, and colleagues discovered that a probiotic consisting of both Lactobacilli genus and Bifidobacteria helped to alleviate hay fever symptoms and improved quality of life during allergy season. They published their findings in the American Journal of Clinical Nutrition.
The team enrolled 173 healthy adults, all of whom had mild to moderate seasonal allergies. The participants were then randomly allocated to one of two groups. One group was given the combination probiotic in the form of a capsule, to be taken twice daily, while the other group received a placebo.
Participants were not using any other allergy medications during the eight-week study period. The study took place during the peak of spring allergy season. As compared to those who took the placebo, the participants with the probiotic reported reduction in allergy symptoms and a better quality of life.
“Not all probiotics work for allergies. This one did,” Dennis had told the British site, Medical News Today, at the time.
However, studies are still ongoing to see precisely how this combination probiotic might reduce symptoms of seasonal allergies.
The benefits of probiotics and prebiotics
“Probiotics have shown promise in promoting gut health and balancing the microbiome. Some studies suggest that the use of probiotics may help modulate the immune response and alleviate hay fever symptoms. Additionally, maintaining a diet rich in fiber, prebiotics, and fermented foods can nurture a diverse gut microbiome,” Dennis says.
On the other hand, prebiotics are fibres that help stimulate beneficial bacteria in the gut. And so, the good bacteria feed on prebiotics. Both of these are important for maintaining a healthy gut microbiome.
For example, Lactobacillus acidophilus helps decrease the expression of inflammatory cytokines associated with allergic inflammation in the mucous membranes in the nasal cavity.
Similarly, Lactobacillus rhamnosus GG has been shown to reduce airway hyperesponsiveness, where the airways narrow excessively in response to stimuli, decrease inflammatory cells in the lungs, and reduce inflammatory cytokines.
(According to 2023 research Immunity, Inflammation and Disease)
