The aim of this review study was to discuss and highlight the most important risk factors and causes of Inflammatory bowel disease (IBD), through reviewing the relevant evidence. We searched following electronic databases (PubMed and EMBASE) to May 2017. Search strategy targeted relevant studies to our main topic which is Inflammatory Bowel Disease (IBD), using Mesh terms through PubMed as following; “IBD” OR “Crohn's disease (CD)” OR “ulcerative colitis (UC)” combined with “Etiology” AND “Risk factors” AND “Epidemiology” AND “Pathogenesis”. IBD is a growing disease that is pricey to the individual and culture. The underlying property of the hygiene hypothesis is that lowered microbial direct exposure in youth could cause the succeeding advancement of IBD appears to be possible. However, the evidence supporting that genetic, environmental factors and life style, as well as H pylori exposure, are the most factors contributing in causing of IBD.