Shop
-1.png)
eStoreRx™
Online Supplement Dispensary
eStoreRx™ is an easy direct-to-patient ordering & fulfilment program for lifelong wellness.
Emerging research suggests that disturbances in small intestinal microbial balance may influence immune function well beyond the gastrointestinal tract. As a major site of immune education and host–microbiome communication, the gut plays a central role in shaping immune tolerance and inflammatory responses.
A recent review published in the International Journal of Molecular Sciences explored the potential relationship between small intestinal bacterial overgrowth (SIBO) and atopic conditions, including asthma, food allergy, chronic spontaneous urticaria (CSU), and mast cell activation syndrome (MCAS). The authors propose that microbial overgrowth within the small intestine may influence allergic susceptibility through effects on intestinal barrier integrity, endotoxin exposure, and immune signaling pathways.
Atopic disorders are characterized by exaggerated immune responses to otherwise harmless antigens and are often associated with IgE production, eosinophilic activity, mast cell activation, and T-helper 2 (Th2)-dominant immune signaling. While genetics contribute to allergic risk, environmental exposures, diet, and microbial ecology are increasingly recognized as important modulators of immune tolerance.
The review highlights several mechanisms that may link SIBO to atopic manifestations. Bacterial overgrowth can increase exposure to microbial components such as lipopolysaccharide (LPS), disrupting the inflammatory response as well as intestinal barrier function. Increased intestinal permeability may enhance immune exposure to dietary antigens and microbial products, potentially amplifying immune activation.
The authors also describe how microbial overgrowth may stimulate epithelial-derived cytokines – including IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) – which activate type 2 innate lymphoid cells (ILC2s) and promote Th2-skewed immune responses. This signaling cascade increases production of cytokines such as IL-4, IL-5, and IL-13, which play central roles in IgE synthesis, eosinophil recruitment, mucus production, and mast cell activation.
Across the studies reviewed, SIBO prevalence was reported to be highest among individuals with asthma (60–100%) and food allergies (50–87.5%), with lower rates observed in MCAS (30.9%) and CSU (27.9%). However, the authors emphasize that these findings should be interpreted cautiously due to substantial heterogeneity in study design, patient populations, and diagnostic methods.
The review also notes preliminary evidence suggesting that treatment of SIBO may improve symptoms in some patients with asthma and MCAS, although current data remain limited and do not establish a causal relationship.
Collectively, these findings support the concept of a "gut–allergy axis," in which microbial balance, intestinal barrier function, and immune signaling interact within an integrated physiological network. While it remains unclear whether SIBO contributes directly to atopic disease or reflects a shared underlying disturbance in immune and barrier function, this emerging body of research highlights the importance of considering gastrointestinal health within a broader systems-based framework of immune regulation. Further prospective studies are needed to clarify the clinical significance of this relationship and determine whether addressing microbial imbalances may influence allergic disease outcomes.
Submit your comment