The aim of the investigators' study is to evaluate biochemical, immunological and histological characteristics of patients affected with the so-called gluten (or wheat) sensitivity who suffers from irritable bowel syndrome (IBS)-like symptoms. As it is not known what component of the cereals causes the symptoms in so called gluten-sensitive patients, the investigators prefer to speak of not-celiac wheat sensitivity (NCWS). NCWS patients may be defined as ones, neither celiac or allergic to wheat, who develop symptoms following wheat consumption, that improved on wheat/gluten free diet (GFD). For our research, we will select adult patients, both genders, affected with suspected NCWS (i.e. with symptoms/signs which disappeared on GFD and worsen on a gluten containing diet, testing negative for celiac disease \[anti-tissue transglutaminase antibodies, anti-tTG, and anti-endomysium antibodies, EMA, and with biopsy Marsh 0-1\] and wheat allergy \[serum specific IgE for wheat\]). The patients will be recruited at the Department of Internal Medicine, 'Giovanni Paolo II' Hospital of Sciacca (Agrigento), and of Internal Medicine of the University of Palermo, from January 2012 to October 2013, for IBS-like symptoms. At the time of the recruitment, the patients will be on GFD by at least one month and must be asymptomatic. A more restricted elimination diet (with the exclusion of cow's milk, egg and other foods) could be prescribed in patients who are suspected to suffer from multiple food hypersensitivity. The patients will be randomized to undergo a double-blind placebo-controlled study, assuming wheat flour or placebo, administered daily for 15 days. Before and after the challenge, the investigators will evaluate gastrointestinal (Gastrointestinal Symptom Rating Scale, GSRS) and the investigators will collect blood and fecal sampling and biopsies from endoscopic evaluation (both esophagogastroduodenoscopy and rectoscopy, with multiple biopsies), for the identification of possible markers (serological, biochemical, immunological, histological features, expression of cytokines and other constitutive mucosal proteins from peripheral blood mononuclear cells, mucosal lymphocytes and fecal biomarkers) that may be of help to diagnose the condition of NCWS and to understand its pathogenesis.