Probiotics have been proposed as useful therapeutic alternatives for the treatment of irritable bowel syndrome patients. Bacillus clausii is a probiotic that has been used for the treatment of acute diarrhea among adults and pediatric patients, as well as an adjunctive therapy for the treatment for Helicobacter pylori infection. It has been proposed that Bacillus clausii is effective for the treatment of irritable bowel syndrome-related symptoms (especially diarrhea and bloating) in non-controlled trials. The aim of the proposed investigation is to determine whether the administration of Bacillus clausii during two weeks plus dietary advice compared to antispasmodics plus dietary advice would be an effective and safe alternative.

Inclusion Criteria:

• Adult patients with non-constipated irritable bowel syndrome according to Rome IV criteria

Exclusion Criteria:

• Allergy to Bacillus clausii spores
• Prior treatment with antibiotics or probiotics (4 weeks)
• Not willing to fulfill symptom diary
• Pregnancy or breastfeeding
• Clinical suspicion of organic disease