Using confocal laser endomicroscopy (CLE), gastrointestinal allergic reactions to certain foods in the duodenum will be evaluated on a cellular level. After that, a personalized exclusion diet will be followed based on the CLE results for 6 weeks, sham-controlled, in a cross-over fashion. Gastroscopy with esophageal biopsies will be repeated after each diet.

Eosinophilic esophagitis is an antigen driven esophagitis, that is characterized by symptoms of dysphagia often leading to food impaction, and that leads to strictures and esophageal motility disorders, with a significant impact on quality of life. Current treatment options include proton pump inhibitors (PPI's) and topical steroids, and also the empiric 6-food elimination diet (6FED). In this diet, the 6 most frequently implicated foods are excluded and reintroduced one by one (milk, gluten containing grains, egg, soy, nuts, fish & shellfish). However, this is a complicated and long process, including several endoscopies with esophageal biopsies.

Confocal laser endomicroscopy (CLE) is a technique that allows to detect gastrointestinal allergic reactions in the duodenum, and to visualize them on a molecular level in real-time. The CLE probe is passed through the working channel of a standard gastroscope, up against the duodenal mucosa. After intravenous injection of fluorescein as contrast medium, the duodenal epithelium is visualized on a cellular level, including food protein mediated extravasation of fluorescein into the lumen. The 6 foods of the 6FED are sprayed on the epithelium one by one, after which a reaction is awaited. Previous use of CLE has shown that more than half of Eosinophilic esophagitis (EoE) patients reacts to one or more foods during CLE.

In this double blind randomized cross-over study the effect a personalized elimination diet, based on the reaction during CLE, is compared to a sham diet, in patients with eosinophilic esophagitis, and insufficient response or intolerance to PPI's. Both diets will be followed for 6 weeks, after which gastroscopy with esophageal biopsies will be repeated. Patients that do not have a reaction to the 6 foods will act as controls, following a control diet with milk and gluten in a cross-over fashion.

Inclusion Criteria:

• Eosinophilic Esophagitis, with peak eosinophil count of >15 eos/HPF and symptoms of dysphagia at least 2 days per week
• Patients have had a trial of high-dose PPI for at least 8 weeks, with either documented non-response or intolerance to the medication
• Patients aged between 18 and 70 years old
• Signed written informed consent
• Eosinophilic Esophagitis, with peak eosinophil count of >15 eos/HPF and symptoms of dysphagia at least 2 days per week
• Patients have had a trial of high-dose PPI for at least 8 weeks, with either documented non-response or intolerance to the medication
• Patients aged between 18 and 70 years old
• Signed written informed consent

Exclusion criteria:

• IgE-mediated food anaphylaxis for 1 of the trigger nutrients
• History of major gastrointestinal surgery complicating esophago-gastro-duodenoscopy
• Gastro-esophageal reflux disease (GERD) Los Angeles grade C or D
• Esophageal strictures, too narrow to pass with a normal gastroscope
• Endoscopic dilation in the esophagus in the 4 weeks prior to inclusion
• Celiac disease
• Recent use (within two weeks) of non-steroidal anti-inflammatory drugs (NSAIDs), systemic histamine-receptor antagonists, mast cell stabilizers, opioids.
• Proton pump inhibitors must be either stopped for at least 4 weeks, or continued on a stable dosage throughout the study period.
• Corticosteroids should be stopped for at least 4 weeks.
• Allergy to fluorescein, Xylocain or Propofol
• Pregnant or lactating women

Nor the participant, nor the primary or secondary investigators involved in the study will know to which nutrients the patient reacted as assessed by CLE, nor will they know what the order of the diet is (sham or real). An investigator who did not participate in the CLE will give dietary instructions.