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Conventional wisdom holds that exposure to dirt and germs is bad for one’s health: after all, ‘cleanliness is next to godliness.’ More recently, the high prevalence of immune-mediated diseases in industrialized countries (with relatively high standards for cleanliness and sanitation) has called this notion into question. The ‘hygiene hypothesis’ proposes that the increasing incidence of immune-related disorders results from reduced exposure to microbes in early childhood. Indeed, previous research has shown that animals that are susceptible to autoimmune disease are more likely to develop disease (and their disease is more severe) when they are raised in germ-free conditions than when they are exposed to bacteria. Now, a new study by Denise Kelly (University of Aberdeen, UK) and colleagues establishes a direct link between microbe exposure and immune health.
Lab Anim. (NY) 39, 2 2010.
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