RESUMO
INTRODUCTION AND BACKGROUND: Multiple chemical sensitivity (MCS) is a complex clinical entity that includes a large number of non-specific symptoms, associated in a univocal manner in each patient and triggered by exposure to various chemicals at low concentrations, well below those known to cause toxic effects. However, no objective test exists currently to diagnose this syndrome. One of the main reasons is that the pathophysiology is poorly understood. However, many explanatory hypotheses have been proposed. VIEWPOINTS AND CONCLUSIONS: Patients with symptoms of MCS are often encountered by pulmonologists. Their suffering is undeniable but, unfortunately, the lack of understanding of the pathophysiological mechanisms makes treatment difficult and empirical.