Endotoxin: friend or foe?

Endotoxin in our living environment has been of increasing interest to our global community of allergists. Initially and largely studied for its capacity to mediate septic shock (and earning its "-toxin" suffix), we have since come to understand that endotoxin in the dust of many occupational settings also is an occult respiratory culprit, inducing airflow obstruction and aggravating asthma and allergies. More recently, environmental endotoxin has been implicated as a microbial exposure in early childhood that may have an atopy-protective effect by augmenting early Th1-type immune development. Although seemingly paradoxical, endotoxin's dual nature ultimately may serve to enlighten our understanding of how such bioactive exposures can interact with and guide our immune systems in both health and disease.