Inflammatory bowel disease (IBD) is a chronic, relapsing gastrointestinal disease that currently affects a total of approximately 28 million people worldwide (cite) . Although not considered a life-threatening disease, the painful and disabling symptoms can have a profound detrimental effect on patients' quality of life. Current knowledge of the etiology of IBD emphasizes genetic predispositions to imbalances in the gastrointestinal immune system. However, pathophysiological insights into IBD appear limited as explanatory tools given the distribution of IBD cases in industrialized and non-industrialized countries. Therefore, this article will provide an overview of the biological aspect of IBD as well as the main environmental factors of the disease. Of greatest concern will be the role of helminth eradication in industrialized countries, consistent with the hygienic hypothesis of autoimmune diseases. Other lifestyle factors, such as diet, smoking and occupation, will also be covered. Overview of IBD immunogenetics. IBD is a group of chronic disorders that cause inflammation of the gastrointestinal (GI) tract. It is generally divided into two categories: ulcerative colitis and Crohn's disease. A main difference between the two categories is that ulcerative colitis is characterized by more superficial colonic inflammation that affects the mucosa and submuscularly, while Crohn's disease is a more discontinuous transmural inflammation occurring anywhere along the of the gastrointestinal tract. Twin studies provide evidence that there is a genetic predisposition to IBD (cite). Some patients have susceptibility genes that put them at higher risk for both Crohn's disease and ulcerative colitis. Bacteria, which are abundant inside the paper......, 1-9.Podolsky, DK (1991). Inflammatory bowel disease. New England Journal of Medicine, 325(13), 928-937.Rook, GAW (2012). Hygiene hypothesis and autoimmune diseases. Clinical Reviews in Allergy and Immunology, 42(1), 5-15.Sonnenberg, A. (1990). Occupational distribution of inflammatory bowel diseases among German employees. Gut, 31(9), 1037-1040. Soon, S., Molodecky, NA, Rabi, DM, Ghali, WA, Barkema, HW and Kaplan, GG (2012). The relationship between urban environment and inflammatory bowel disease: a systematic review and meta-analysis. Gastroenterology BMC, 12(1), 51. Turan, MT and Besirli, A. (2008). Impacts of the urbanization process on mental health. Anatolian Journal of Psychiatry, 9, 238-243. Weinstock, JV and Elliott, DE (2009). Helminths and the hygiene hypothesis of IBD. Inflammatory bowel diseases, 15(1), 128-133.