Background and study aims Gastrointestinal symptoms assumed to be caused by
food intolerance are reported frequently in the general population. There is a significant difference between self-reported and objective proven
food intolerance, as shown by placebo-controlled, double-blind, randomized trials. This discrepancy may be overcome by endoscopic confocal
laser endomicroscopy (eCLE). Patients and methods In an observational study we evaluated 34 patients with functional
abdominal pain and adverse reaction to food by eCLE and local duodenal food challenge for the first time. Spontaneous and food-induced transfer of
fluorescein into the duodenal lumen was detected 10 minutes after intravenously application of
fluorescein and 10 minutes after duodenal food challenge (DFC). Results Of the patients, 67.6 % responded with a
fluorescein leakage into the duodenal lumen. Frequency rank order of food
antigens that induced a response were soy (50 %), wheat (46.1 %), milk (20 %), egg (12 %), and yeast (11.5 %), respectively. Of the patients, 23.5 % showed spontaneous leakage of
fluorescein, suggesting leaky gut syndrome. Histology of duodenal biopsies and mast cell function were normal. Overall, 69.5 % of patients improved with food exclusion
therapy and 13 % were symptom-free according to eCLE. Conclusions The results of our study indicate that eCLE is a clinically useful tool to evaluate patients with functional
abdominal pain and adverse reaction to food and to create individualized dietary
therapy with clinical benefit for patients.