1. The Connection Between the Gut and Allergies
The gut hosts a highly complex ecosystem of bacteria, fungi, and other microbes – the gut microbiome. This system is in constant interaction with the immune system and influences how the body responds to pollen, food, or house dust – stimuli that are mistakenly classified as dangerous in allergies, leading to an exaggerated immune response.
Studies show:
Dysbiosis – an imbalance of the gut microbiome – is associated with various allergies, including hay fever, asthma, and food allergies.
The microbiome acts as a “trainer” of the immune system and influences the balance between different immune cells involved in allergic responses.
A disrupted gut microbiome is linked to increased intestinal permeability (“leaky gut”); as a result, more allergens and microbial components can enter the body and amplify immune reactions.
In short:
A well-balanced microbiome (eubiosis) helps counteract allergies, whereas dysbiosis may promote them.
2. Microbiome – Immune System – Allergy: The Basic Principle
The interplay between the microbiome, the immune system, and allergies can be clearly described:
The microbiome produces molecules such as short-chain fatty acids (SCFAs = short-chain fatty acids).
SCFAs can influence immune cells and exert anti-inflammatory effects.
They can strengthen specific immune cells, known as regulatory T cells, and reduce excessive reactions of other immune cells (Th2 cells).
If this balance is disrupted, harmless stimuli such as pollen, food, or animal hair are more likely to trigger an immune response. In this process, the body produces increased levels of immunoglobulin E (IgE) – a specific type of antibody involved in allergic reactions – leading to an excessive release of histamine.
The question of why some individuals develop hay fever or food allergies while others do not, despite similar environmental exposure, is largely related to the microbiome and the barrier function of the gut, lungs, and skin.
3. Hay Fever & Gut Microbiome: What Research Shows During Pollen Season
Clinical studies show that a combination of probiotics and prebiotics can lead to noticeably reduced symptoms, improved immune parameters, and increased levels of short-chain fatty acids such as acetate.
In addition, probiotics can significantly improve both symptoms and quality of life in allergic rhinitis by shifting the balance between certain immune cells (Th1/Th2 ratio) toward a more balanced immune response.
Specific probiotic formulations have also proven beneficial during the pollen season, with improvements not only in symptoms but also in factors such as sleep quality and fatigue.
Conclusion:
Targeted use of probiotics and prebiotics can positively influence hay fever – not directly in the nasal passages, but through modulation of the immune system and the gut microbiome.
Important: Effect depends on probiotic strains, dosage, and duration.
4. Leaky Gut & “Gut Conditioning in Allergies”
The term “leaky gut” describes the relationship between intestinal barrier function and allergies:
The intestinal epithelium, together with tight junctions, a mucus layer, and immune cells, forms a highly organized protective barrier.
Tight junctions are “sealing proteins” in the intestinal wall. If they fail to function properly, the intestinal barrier becomes permeable to harmful substances, resulting in a “leaky gut.”
In the presence of dysbiosis, this barrier may be weakened; permeability increases, allowing more allergens to reach the immune system.
Review studies emphasize that increased intestinal permeability may contribute to allergic sensitization – particularly in food allergies.
Scientifically, “gut conditioning” in the context of allergies includes:
- Supporting the microbiome (e.g., through probiotics/prebiotics)
- Strengthening barrier function
- Modulating the immune response toward greater tolerance or more effective control of allergic reactions
Several scientific reviews consider this a promising complementary approach, although not a cure.
5. Gut–Lung Axis & Asthma
The gut–lung axis describes how the gut can influence respiratory responses:
Reviews show that the gut microbiome and its metabolic products (including SCFAs) can influence immune responses in the airways and modulate inflammatory reactions in allergic asthma.
Dysbiosis and impaired barrier function are associated with increased inflammatory activity, oxidative stress, and heightened airway reactivity.
Probiotics and prebiotics are being explored as approaches to positively influence immune balance, barrier function, and respiratory health via the microbiome.
The gut–lung axis is therefore increasingly regarded as a relevant target for future therapeutic strategies.
6. Practical Implications (without medical claims)
Gut–Allergy Connection
The microbiome influences how the immune system responds to allergens.
Dysbiosis is associated with hay fever, asthma, and food allergies.
Leaky Gut & Allergy
A weakened intestinal barrier facilitates the passage of allergens and promotes allergic reactions – particularly in food allergies.
Gut–Lung Axis & Asthma
SCFAs influence inflammatory processes in the airways; microbiome-based approaches are being actively researched.
Probiotics & Gut Conditioning in Allergies
Probiotics (often combined with prebiotics) may improve symptoms and quality of life and positively modulate immune markers.
However, they do not replace conventional therapies or allergen avoidance.
