CRH and irritable bowel syndrome: Interestingly, preclinical studies have identified increased intestinal permeability as the potential link between psychological stress and mucosal immune activation via enhanced passage of antigens,10 with improvement after probiotics.11,12 Increased intestinal permeability has been demonstrated in IBS and IBD with mucosal eosinophil and/or mast cell activation.13,14 We showed that a social-evaluative stressor (public speech) and intravenous administration of CRH increased small intestinal permeability quantified by the urinary lactulose-to-mannitol ratio (LMR) in healthy students.