Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder; it is also one of the most commonly diagnosed gastrointestinal diseases. The worldwide prevalence of IBS ranges from 10% to 20% with an estimated incidence of 1.4–1.5%, according to longitudinal population-based study lasting 10-12 years.1,2 IBS is more common in women and in young adults. The clinical manifestation of IBS is not unique; however, it can be classified into three subtypes. IBS subtypes include constipation-predominant (IBS-C), diarrhea-predominant (IBS-D), and IBS with predominant irregular (mixed diarrhea/ constipation) bowel habits (IBS-M). IBS subtyping is more accurate when patients have at least 4 days of abnormal bowel habits monthly in the absence of any specific treatment such as laxatives or antidiarrheal agents using a diary report of at least 14 days. An alteration in stool consistency (i.e. hard/lumpy stools or loose/watery stools) for more than 25% of bowel movements is the threshold for classification in the various IBS subtypes.