Multiple chemical sensitivity: A 1999 consensus

Consensus criteria for the definition of multiple chemical sensitivity (MCS ) were first identified in a 1989 multidisciplinary survey of 89 clinicians and researchers with extensive experience in, but widely differing views o f, MCS. A decade later, their top 5 consensus criteria (i.e., defining MCS as [1] a chronic condition [2] with symptoms that recur reproducibly [3] in response to low levels of exposure [4] to multiple unrelated chemicals and [5] improve or resolve when incitants are removed) are still unrefuted in published literature. Along with a 6th criterion that we now propose adding (i.e., requiring that symptoms occur in multiple organ systems), these cri teria are all commonly encompassed by research definitions of MCS. Nonethel ess, their standardized use in clinical settings is still lacking, long ove rdue, and greatly needed-especially in light of government studies in the U nited States, United Kingdom, and Canada that revealed 2-4 times as many ca ses of chemical sensitivity among Gulf War veterans than undeployed control s. In addition, state health department surveys of civilians in New Mexico and California showed that 2-6%, respectively, already had been diagnosed w ith MCS and that 16% of the civilians reported an "unusual sensitivity" to common everyday chemicals. Given this high prevalence, as well as the 1994 consensus of the American Lung Association, American Medical Association, U .S. Environmental Protection Agency, and the U.S. Consumer Product Safety C ommission that "complaints [of MCS] should not be dismissed as psychogenic, and a thorough workup is essential," we recommend that MCS be formally dia gnosed-in addition to any other disorders that may be present-in all cases in which the 6 aforementioned consensus criteria are met and no single othe r organic disorder (e.g., mastocytosis) can account for all the signs and s ymptoms associated with chemical exposure. The millions of civilians and te ns of thousands of Gulf War veterans who suffer from chemical sensitivity s hould not be kept waiting any longer for a standardized diagnosis while med ical research continues to investigate the etiology of their signs and symp toms.