Question: How Does The Hygiene Hypothesis Relate to IBD?
Answer: The hygiene hypothesis has been discussed as one reason that industrialized societies might have high rates of autoimmune diseases, such as inflammatory bowel disease (IBD). The idea is that Western countries are "too clean" and our immune systems are not challenged enough early on, which can lead to chronic diseases. Societies whose children have more exposure to bacteria and germs tend to have fewer incidences of autoimmune disease.
The hygiene hypothesis has been put forth as one of the potential causes of IBD. Wanting to see how the hygiene hypothesis relates to IBD, I checked out the article about environmental factors and IBD on UpToDate -- an electronic reference used by many physicians and patients looking for in-depth medical information.
"...some environmental factors may be protective against the development of IBD. Some studies suggest that contact with farm animals during early life reduces the likelihood of developing IBD. The effect sizes were small, and other studies concluded that pet exposure has the opposite effect. Nonetheless, the observations are consistent with the hypothesis that exposure to infectious pathogens early in life confers protection against some immune-mediated diseases (the "hygiene hypothesis")."
Some studies have shown that people who are exposed to farm animals in infancy have less risk of developing Crohn's disease or ulcerative colitis. Other studies have been done that do not show this link, further complicating the issue of whether the hygiene hypothesis is indeed a cause of IBD and other autoimmune diseases.
While some research shows that developed countries may be "too sterile," infant mortality in developed societies is significantly lower than it is in less developed societies. No one is suggesting that access to clean water, clean air, and fresh food should be forgone in the hopes of banishing autoimmune disease, but researchers are working on a compromise. Studies are being done where certain bacteria are introduced into the digestive tract in the hopes of developing a new treatment for the symptoms of IBD.
Want to learn more? See UpToDate's topic, "Epidemiology and environmental factors in inflammatory bowel disease in children and adolescents," for additional in-depth medical information.
Higuchi, Leslie M and Bousvaros, Athos. "Epidemiology and environmental factors in inflammatory bowel disease in children and adolescents." UpToDate. Accessed: May 2010.