Science Daily, March 22, 2012
Summary: Medical professionals have suggested that the hygiene hypothesis explains the global increase of allergic and autoimmune diseases in urban settings. However, neither biologic support nor a mechanistic basis for the hypothesis has been directly demonstrated. Until now.
This concept of exposing people to germs at an early age (i.e., childhood) to build immunity is known as the hygiene hypothesis. Previous human studies have suggested that early life exposure to microbes (i.e., germs) is an important determinant of adulthood sensitivity to allergic and autoimmune diseases such as hay fever, asthma and inflammatory bowel disease.
Medical professionals have suggested that the hygiene hypothesis explains the global increase of allergic and autoimmune diseases in urban settings. It has also been suggested that the hypothesis explains the changes that have occurred in society and environmental exposures, such as giving antibiotics early in life.
Researchers at Brigham and Women's Hospital (BWH) have conducted a study that provides evidence supporting the hygiene hypothesis, as well as a potential mechanism by which it might occur.( The study was published online in the journal Science on the Science Express Web site on March 22, 2012.) . The researchers studied the immune system of mice lacking bacteria or any other microbes ("germ-free mice") and compared them to mice living in a normal environment with microbes. They found that germ-free mice had exaggerated inflammation of the lungs and colon resembling asthma and colitis, respectively. This was caused by the hyperactivity of a unique class of T cells (immune cells) that had been previously linked to these disorders in both mice and humans.
Most importantly, the researchers discovered that exposing the germ-free mice [when young], led to a normalized immune system and prevention of diseases.
Source: The above story is based on materials provided by Brigham and Women's Hospital. Materials edited for content and length as published in www.sciencedaily.com