## 4 Discussion  
CLE is a rapidly evolving field in gastroenterology that bridges endoscopy and histology, enhancing the ability to visualize living tissues in real-time and provide therapies within the same setting [34]. Moreover, CLE has the privilege of being able to evaluate in real-time some functional dynamics related to barrier integrity (e.g., cell shedding, fluorescein leakage) that do not have any histological counterpart. Several studies demonstrate how CLE can serve as an innovative diagnostic tool capable of providing an immediate correlation between mucosal alterations and clinical response, leading to a personalized approach to intestinal symptoms triggered by food, regardless of the etiological hypothesis. The evidence in this field is still limited. The study conducted by [PERSON] et al. [36] appears to be unique in applying CLE to directly investigate intestinal barrier dysfunction in patients with suspected FA, including patient stratification based on barrier integrity parameters for further diagnostic workup. Alterations were also reported in 33% of non-FA patients who experienced gastrointestinal symptoms not directly linked to specific food consumption (\(p<0.0001\)). Crypt architecture parameters (crypt diameter, inter-crypt distance, and lumen diameter) did not differ significantly between FA and non-FA groups [36]. Other studies [38; 39; 42; 43; 44; 45; 46] have explored similar concepts in the context of IBS patients who tested negative for IgE. In these studies, CLE was used to assess intestinal barrier integrity, with a focus on direct stimulation with food antigens and subsequent dietary interventions based on the observed results [38; 39; 40; 41; 43; 44; 45; 46]. Alterations in the distribution of key proteins, such as occludin and claudin-1, have already been associated with increased intestinal permeability in IBS patients [47]. This finding has been further supported by hypotheses formulated in the study by [PERSON], which linked intestinal barrier defects observed through CLE with alterations in these proteins [39]. The authors suggested that the observed reactions could be mediated by local immune responses of the duodenal mucosa in response to commonly used food antigens such as wheat [38; 39; 41; 43] which was the most frequent cause of positive food challenge tests in the reported studies. This finding is further supported by other studies [48; 49; 50] which report the benefits of a gluten-free diet in patients with functional gastrointestinal symptoms and negative for celiac disease through the concept of non-celiac gluten sensitivity [51]. However, some authors discourage using CLE for diagnosing this condition due to its low specificity, which does not justify its use as an invasive initial test in IBS patients suspected of wheat sensitivity [52]. Nevertheless, CLE may help elucidate the pathomechanisms underlying mucosal and submucosal changes during food-induced gastrointestinal alterations [52]. The mucosal barrier alterations observed in GARF\(-\) patients in [PERSON]'s study are particularly noteworthy [41]. The study analyzed a heterogeneous group of patients with functional gastrointestinal symptoms. This broad categorization encompassed a diverse population, potentially including patients with IBS. Intestinal barrier disruptions, such as fluorescein leakage, were identified in both GARF\(+\) and GARF\(-\) patients, indicating that mucosal damage is not exclusive to those with a clear food-symptom correlation. However, 74% of GARF\(-\) patients exhibited mucosal alterations but only 14% improved with dietary intervention underscoring CLE's low specificity (68%) and therefore its inadequacy as a standalone diagnostic tool. The different sizes of both groups might cause some bias, therefore, to prove the results by a larger group of patients GARF\(-\)is needed.