A study conducted by the Saul Krugman Division of Pediatric Infectious Diseases and Immunology, New York University School of Medicine, New York, New York published in the June 2012 issue of Pediatric Allergy, Immunology, and Pulmonology found that, “Early-life exposures to microbes, coupled with genetically determined susceptibility, have an impact on the natural history of childhood asthma. We hypothesized that childhood infection with Mycobacteria tuberculosis, a bacterium that has infected Homo sapiens for close to millennia, may be relevant to the risk of asthma development. The aim of this study was to evaluate any associations between tuberculosis infection with asthma and allergies using the cross-sectional and the U.S. nationally representative 1999–2000 National Health and Nutrition Examination Survey… Children under twenty years of age infected with tuberculosis were significantly less likely to have a history of asthma or symptoms of asthma over the prior year than children not infected with tuberculosis. This finding was not confounded by bacille Calmette-Guerin vaccination. Tuberculosis infection is associated with a substantially decreased risk of asthma in children. This finding is consistent with the hygiene hypothesis, which suggests that microbes that co-evolved with humans may influence developing immune systems in ways that have a protective effect against the development of asthma.” To read the study, click here.