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