## 5 Conclusions  
CLE is an emerging technology with significant potential for evaluating intestinal barrier alterations, both in patients with classic food allergies and in those with functional gastrointestinal disorders such as IBS. Current data suggest that intestinal barrier dysfunction may represent a shared pathophysiological mechanism between FA and IBS, highlighting the need for further research to elucidate the connections between these two conditions. Specifically, it would be valuable to determine whether the alterations detected by CLE are specific markers for allergies or a more general phenomenon associated with intestinal disorders. CLE is not limited to the identification of classic food allergies but offers a unique opportunity to investigate the role of local intestinal barrier dysfunctions in non-IgE-mediated conditions, expanding its utility beyond traditional diagnostic applications. IELs, in a process partly mediated by the secretion of interferon-gamma [68], likely enhance epithelial permeability by activating myosin light chain kinase, leading to phosphorylation of myosin light chains within the contractile actomyosin ring of the tight junctions. This results in a redistribution of tight junction proteins such as occludin and claudins [69]. For instance, CLE has shown preliminary findings suggest the occurrence of acute reactions in other conditions such as functional dysppesia, eosinophilic esophagitis, and inflammatory bowel disease [70; 71; 72; 73] The mucosa of the ileum and colon have been analyzed in some studies investigating intestinal permeability in patients with inflammatory bowel disease (IBD), but without stimulation tests using food antigens. Furthermore, an important aspect of these studies lies in the ability to correlate previously described IBS characteristics, such as increased TRPV channel expression or altered distribution of junctional proteins that regulate intestinal barrier permeability, with direct stimulation through food mixtures [39; 42]. Future developments in this technique could include real-time correlation of observed mucosal changes with findings from transcriptomic studies, thereby deepening the understanding of molecular mechanisms involved in functional gastrointestinal disorders. One of the main findings was correlated with transcriptomic analyses, which revealed a significant reduction in claudin-1 protein expression [70]. This approach offers an innovative perspective, enabling not only the identification of mucosal alterations in response to food antigens but also their direct correlation with clinical symptoms reported by patients. However, it is important to acknowledge the limitations of these studies. The available literature linking clinical outcomes to acute reactions identified via CLE is limited, mostly uncontrolled and unblinded, and often conducted on heterogeneous patient populations [74]. Many studies have involved small sample sizes, often in single-center settings, with limited observation periods, particularly during post-elimination diet phases. Additionally, despite being a highly useful tool, CLE has significant challenges: it is expensive, technically demanding, and requires prolonged sedation. CLE is also currently available only in a few specialized centers. These factors limit the generalizability and applicability of such studies in routine clinical practice. Despite these limitations, these studies provide a starting point for better understanding IBS pathophysiology. CLE could potentially form the basis for developing standardized therapeutic strategies aimed at reducing symptoms through targeted and personalized interventions. Moreover, an improved understanding of the underlying mechanisms could help reduce the economic burden on healthcare systems by decreasing the need for frequent specialist visits and unnecessary diagnostic tests.