Model development and research vision for the future of multiple chemical sensitivity

Multiple chemical sensitivity (MCS) is characterized by heightened self-rep orted sensitivity to extremely low concentrations of chemicals. It has nume rous symptoms in common with the sick building syndrome, the Gulf War syndr ome, and chronic fatigue. Despite much research, reproducible objective fin dings are lacking for MCS, as is a sound model to explain it. This paper pr oposes a 2-step model combining the needed epidemiologic terminology with t hat of psychophysiological activation and sensitization. It is suggested th at different environmental stressors act as initiators. After initiation, t he limbic system and other parts of the brain become sensitized and hyperac tive to environmental triggers. Odor acts as one important trigger. Future research should use more biological assessments in combination with environ mental and psychosocial data and involve patient groups with similar sympto ms, although diagnosed as suffering from different entities. The similariti es and differences of patients with such entities need to be understood bef ore the entities themselves can be understood, diagnosed, treated, and prev ented.