RESEARCH ARTICLE

Full list of author information is available at the end of the articleBackground Asthma is a chronic respiratory disease that can lead to activity limitation, school and work absenteeism and hospitalization. The environment plays an important role in the development of asthma and in triggering symptom exacerbations although the impact of many environmental exposures remains poorly characterized. One such exposure reported to be associated with asthma or respiratory symptoms is endotoxin. Endotoxin is derived from the cell wall of gram-negative bacteria and is ubiquitous in the environment. It can be pro-inflammatory [1] when encountered as part of a pathogen but can also modify the immune response to potentially protect against atopic disease [2]. Animal models have shown differential allergic responses to endotoxin depending on the timing of exposure [3]. Asthma prevalence has been found to be lower in rura