Multiple chemical sensitivities: distinguishing between psychogenic and toxicodynamic.

The fundamental issue in the multiple chemical sensitivity (MCS) debate is whether this phenomenon is primarily a psychogenic or toxicodynamic disorder, that is, whether symptoms are due to an emotional response to perceived chemical toxicity or to a pathological interaction between chemical agents and organ systems. The distinction between psychogenic or toxicodynamic is essential to the medical management of an MCS patient. A behavioral origin leads to a behavioral therapy, whereas a toxicodynamic etiology may necessitate avoidance and exposure control methodologies. Regulatory, legislative, judicial, and occupational control responses are also dependent upon the critical distinction between psychogenic and organic etiologies. If people are being poisoned by low levels of chemicals, one set of responses follows. If, on the other hand, MCS sufferers are symptomatic for emotional reasons, the response is different. Everything that is known about MCS to date strongly suggests behavioral and psychogenic explanations for symptoms. The premature use of the term multiple chemical sensitivities has hampered effective exploration of and response to this phenomenon, because it suggests, to the lay person, a physiological explanation. It is time that this disorder be properly characterized so that sufferers receive the care they need and so that new "victims" are not recruited.