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World J Gastroenterol. Jan 14, 2008; 14(2): 165-173
Published online Jan 14, 2008. doi: 10.3748/wjg.14.165
Hygiene hypothesis in inflammatory bowel disease: A critical review of the literature
Natasha A Koloski, Laurel Bret, Graham Radford-Smith
Natasha A Koloski, Laurel Bret, Graham Radford-Smith, Department of Gastroenterology, Royal Brisbane & Women’s Hospital, Herston Queensland 4072, Australia
Correspondence to: Graham Radford-Smith, MD, PhD, Department of Gastroenterology, Royal Brisbane & Women’s Hospital, Herston Queensland 4072 Australia. graham.radford-smith@qimr.edu.au
Telephone: +61-7-33620171
Fax: +61-7-36364366
Received: August 31, 2007
Revised: November 18, 2007
Published online: January 14, 2008

The hygiene hypothesis is thought to be a significant contributor to the growing incidence of inflammatory bowel disease (IBD) around the world, although the evidence for specific factors that underlie the hygiene hypothesis in IBD is unclear. We aimed to systematically review the literature to determine which hygiene-related factors are associated with the development of IBD. Publications identified from a broad based MEDLINE and Current Contents search between 1966 and 2007 on key terms relevant to the 'hygiene hypothesis' and IBD including H pylori exposure, helminths, cold chain hypothesis, measles infection and vaccination, antibiotic use, breastfeeding, family size, sibship, urban upbringing, day care attendance and domestic hygiene were reviewed. The literature suggests that the hygiene hypothesis and its association with decreased microbial exposure in childhood probably plays an important role in the development of IBD, although the strength of the supporting data for each of the factors varies considerably. The most promising factors that may potentially be associated with development of IBD include H pylori exposure, helminths, breastfeeding and sibship. However, the vast majority of studies in this area are plagued by serious methodological shortcomings, particularly the reliance on retrospective recall of information making it difficult to truly ascertain the importance of a 'hygiene hypothesis' in IBD. The 'hygiene hypothesis' in IBD is an important area of research that may give clues to the aetiology of this disease. Directions for future research are recommended.

Keywords: Inflammatory bowel disease, Hygiene hypothesis, Microbial exposure, Cold chain hypothesis, H pylori, Helminths, Measles, Antibiotic, Breastfeeding, Child care