The overarching goal of this study is to establish a first ever registry in the U.S. to collect outcomes data to evaluate changes in the gastrointestinal (GI) mucosa following direct food application utilizing Confocal Laser Endomicroscopy (CLE). This will be assessed in pediatric and adult patients who present to the outpatient clinic with persistent irritable bowel syndrome-like symptoms while testing negative for celiac disease and have either negative or very low/low levels of Immunoglobulin E (IgE) serological tests.

The prevalence of food allergies in children and adults are estimated to be 5-7% and 11% in the US respectively. The mechanism underlying food allergies are either IgE mediated, non-IgE mediated or both.

CLE is a diagnostic modality that allows for high-resolution imaging of the GI tract, providing real-time in-vivo visualization of the mucosal and submucosal microstructure similar to histology. What differentiates it from conventional histology wherein tissue is sectioned vertically, is that the endomicroscopic images are a single optical plane parallel to the tissue surface, yielding multiple optical sections of successive depths of greater precision.

Recent studies demonstrated the utility of CLE in the evaluation of gastroenterological diseases, specifically for inflammatory bowel disease. Although histological evaluation continues to remain the gold standard, CLE has potential applications in surveillance, targeted biopsies and disease management of GI conditions such as celiac disease, eosinophilic disease and more recently in patients with Irritable Bowel Syndrome (IBS) with atypical food allergies that are non-IgE mediated.

A common observation in patients with IBS using CLE include increased epithelial gaps when compared to healthy controls. It is proposed that there is an alteration in the epithelial barrier which in healthy state, prevents the microbes and antigens from entering the body. Increased epithelial cell extrusions result in altered intestinal permeability, which is commonly seen in IBS. The utility of CLE in visualizing the integrity of the intestinal barrier in children with atypical presentation of food allergies is unknown. The ability to observe these dynamic changes in real-time is promising in the management of IBS.

Endomicroscopic diagnosis of food-induced allergy-like reactions was first used as a guideline in the implementation of the food intolerance testing performed as part of this protocol.

Inclusion Criteria:

Patients must meet all of the following criteria to be included in the study

• Adults and children presenting with a prolonged history of IBS-like symptoms (as described by Rome IV criteria) related to food intake.
• A negative or very low/low levels of Ig-E food allergy panel or negative skin prick test
• Negative celiac disease work up

Exclusion Criteria:

• If patient had a previous Esophagogastroduodenoscopy (EGD) and Colonoscopy with biopsy positive for any chronic inflammatory condition for eg. Inflammatory Bowel Disease (IBD), the patient will be excluded.
• Pregnant or nursing at the time of CLE.
• Known allergy to fluorescein.
• Impaired renal function tests.
• Active GI bleeding.