No appropriate participants

This study will assess dynamic effects of two major antigens on the duodenal mucosa by confocal laser endomicroscopy (CLE). Patients will be blinded to the antigens used (wheat, yeast). Following CLE it is planned to have a cross over exclusion diet with/without the antigens including a washout phase. Furthermore, patients will undergo a 2 week FODMAP diet to be able to compare results found of both diets and allow to understand whether our findings of food intolerance will be better and more precise than a common FODMAP diet.

Post CLE food challenge patients biopsies will be taken for histology. They will then be randomized into two groups and blinded to the diet they undergo. They will be provided with a supply of custom-made bread they will have for 2 weeks (custom made by a bakery in Kiel). For one study arm bread will contain either wheat and yeast, for the other arm the bread will not contain these ingredients. The taste of the "normal" bread will be denaturised. Crossover will take place after a two-week washout phase.

Inclusion Criteria:

IBS according to the Rome III criteria moderate/severe refractory daily symptoms >1year (FGID-C1) sub classified as IBS-D, constipation predominant (IBS-C) or mixed type (IBS-M) no past infection to trigger symptom no structural/ biochemical cause of their symptoms identified negative gastroscopy, colonoscopy including histology Worsening symptoms after meals various exclusion diets - ineffective females not menstruating during CLE no known allergy to methylene blue or fluorescein Age >18 years Negative routine testing for food intolerance (or known lactose/fructose intolerance) Positive informed consent

Exclusion Criteria:

no consent known reason for the abdominal pain and bloating other than lactose/fructose intolerance M. Whipple Known infectious gastrointestinal disease Stricture in the upper gastrointestinal tract Age <18years Impaired renal function (Creatinine >1.2 mg/dL) Pregnancy or breast-feeding Inability to obtain informed consent Active GI Bleeding Known allergy to Methylene blue or Fluorescein Participation in other clinical trials within the last 4 weeks