The Challenge of Multiple Chemical Sensitivity

Article excerpt


In the 1950s, under the banner of his "clinical ecology" movement, Chicago allergist Theron Randolph proposed what has come to be known as "multiple chemical sensitivity" or MCS (AAAAI Board of Directors, 1999; Whited, 2004). This condition is "an acquired disorder characterized by recurrent symptoms, referable to multiple organ systems, occurring in response to demonstrable exposure to many chemically unrelated compounds at doses far below those established in the general population to cause harmful effects (Cullen, 1987)." Pesticides, cigarette smoke, paint fumes, wood preservatives, office photocopier fumes, perfumes, and epoxy are among the chemically unrelated compounds that commonly trigger MCS ( These in turn produce vague and multisystemic responses which might include any collection of symptoms, such as rapid heart rate, shortness of breath, fatigue, flushing, dizziness, nausea, coughing, or difficulty concentrating (Beers, 2003). As the diversity of causes and manifestations might indicate, MCS is probably best considered not as a single disease but as a class of disorders parallel to infectious or immunologic conditions (Miller, 1997).


MCS has significant psychosocial and economic costs. According to one study, chemical hypersensitivity results in job loss in 13.5% of cases, representing 1.8% of the general population (Caress & Steinemann, 2003). Limited specific information is available on the economic costs of MCS, and it is difficult to quantify objectively and compare the morbidity of many of the symptoms--headaches versus dizziness, for example (The Interagency Workgroup on Multiple Chemical Sensitivity, 1998; Steinemann, 2000). It is difficult, furthermore, to quantify the magnitude of the psychological sequelae that develop (in possibly a third of affected individuals) after onset of physical symptoms (Caress & Steinemann, 2003). The abundant--and at least superficially diverse--effects attributed to chemical sensitivity incorporate significant morbidity and mortality, and economic, healthcare, and social burdens (Gibson, 2005).

A Vague Entity

The study of MCS has shown some evolution over time towards a cohesive and consistent (at least internally) understanding of the disorder. As a social phenomenon, independent of any physiological basis, MCS may be understood in part through the lens of the reactionary response to modern chemicals and hazards (Whited, 2004). Significant difficulty persists, however, in resolving the diverse manifestations and associations into a unifying, underlying disease process. Intensive efforts are ongoing to resolve the inconsistencies of MCS as a class of disorders with the current understanding of disease pathogenesis, encompassing "a profound but little-recognized scientific debate concerning the origins of disease (Miller, 1997)." The history of MCS consists of attempts to address this inconsistency. The resulting conflict, between those who argue that the disease process has an illusive organic basis and those who claim it is entirely psychological or fictitious, remains unresolved.

Given the diverse manifestations and unknown pathogenesis of MCS, no accepted diagnostic physiologic test has been developed, such as complete blood count or antibody levels, which correlates with symptoms (AAAAI Board of Directors, 1999; Beers, 2003). Diagnosis is primarily based on a patient's subjective reports, leading to wide variation in clinicians' assessments (AAAAI Board of Directors, 1999). Diagnosis is further complicated by "masking"--the background of routine exposures which obscures effects of specific chemicals. Even when an MCS-like response is recognized, a specific initiating trigger may not be identified and linked to the patient's ensuing sensitivities. Theoretically, precise diagnosis might require an intensive process in an "environmental medical unit": a controlled setting devoid of triggers, even drinking water. …