The purpose of this study is to evaluate the efficacy of a treatment with Lactobacillus casei DG in the reduction of the painful symptoms in patients affected by irritable bowel syndrome. After that, the secondary object is to evaluate if the reduction of painful symptoms is related to a relevant reduction of trypsin and tryptase in colonic mucosa.

Inclusion Criteria:

• out-Patients with diagnosis of Irritable Bowel syndrome (IBS) according to Rome III Diagnostic Criteria for Functional Gastrointestinal Disorders
• Previous colonoscopy (within 24 month prior the enrollment) with negative results
• written informed consent

Exclusion Criteria:

• systemic or topical therapy with steroids and glucocorticoids such as beclomethasone dipropionate or budesonide, ongoing or within a month prior the enrollment
• therapy with antibiotics or probiotics, ongoing or within a month prior the enrollment
• inflammatory bowel diseases
• copro-paraxitological examination with positive results
• bowel disease with infectious, actinic, endocrine or drug-related origin
• immunodeficiency
• diagnosis of malignant cancer within 5 years prior the enrollment
• renal, hepatic, hematologic, cardiovascular, pulmonary, neurological, psychiatric, immunological, gastrointestinal or endocrine disorders, if found to be clinically relevant
• any severe disease that may interfere with the treatment;
• abuse of alcohol, drugs or medication, psychotropic drugs
• diagnosis of dementia or other disorders that can cause a progressive deterioration of capacity of discernment or mental and physical disability which reduces the ability to follow the prescribed therapy;
• previous participation in this study
• pregnant or nursing (lactating) women