Can bacterial endotoxin exposure reverse atopy and atopic disease?
Can bacterial endotoxin reverse the development of allergies and allergic diseases such as allergic asthma, hay fever and eczema? This is the key question posed in a recent article by Douwes et al in the November 2004 issue of the Journal of Allergy and Clinical Immunology. Studies have shown that childhood exposure to endotoxins – bacterial substances that are commonly present in the environment – is associated with a reduced risk of allergies, including allergic asthma. It is commonly assumed that these effects only occur in early life. However, recent population studies suggest that “immune deviation” may take place throughout life. Assuming that the immune system is not “fixed” after the first years of life, Douwes et al propose that endotoxin exposure may not only inhibit the development of allergies at any time throughout life, but may also reverse this process. This novel extension of the hygiene hypothesis is based on several studies showing a reduction in allergies in adults h
