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Clinicians have been challenged by the individual with multiple complaints relating to low-level occupational or environmental exposures. Patients report respiratory, central nervous system, musculoskeletal, gastrointestinal, and systemic symptoms after exposure to common environmental irritants such as perfumes, cigarette smoke, home or office furnishings, household cleaners, and a host of other petrochemical products. Upper respiratory (eg, nasal congestion, dryness, or burning), central nervous system (eg, concentration problems, memory difficulties, insomnia, drowsiness, irritability, and depression), and vegetative (eg, fatigue, headache, arthralgias, and myalgias) symptoms predominate. Symptoms occur with exposures well below thresholds permitted by federal or state regulatory agencies as causing acute adverse effects in humans, resulting in significant impairment, lost work time, complete job loss, or major alterations in social and family functions. Individuals may report symptom onset following acute or chronic low-level occupational or environmental exposures, with persistent symptoms that are triggered by subsequent environmental contaminants. Often patients seek help from multiple health care providers who suggest psychiatric etiologies or treatment, obtain toxicologic or immunologic test batteries, or initiate a variety of empirical treatments. Workers’ compensation or disability claims often are disputed, and employers may have difficulty accepting or accommodating clinician or patient requests for alternative work environments. As a result, frustration, anger, hostility, and suspicion may confront the clinician when significant impairment continues despite lengthy and expensive consultations.

Some controversy continues to surround the etiology, case definition, diagnosis, and treatment of individuals with multiple chemical sensitivity (MCS). The specialty of clinical ecology that emerged in the 1960s adopted theories of causation that differ from those of traditional allergy, immunology, and toxicology, thereby laying the basis for medical and legal disputes regarding legitimate or acceptable forms of treatment, medical or workers’ compensation insurance reimbursement, and disability benefits. As a result, some clinicians believe that etiologic theories, diagnosis, and the clinical management of MCS are inconsistent with sound medical science. In more recent years, however, important progress has been made in elucidating and defining the nature of this condition. The combined efforts of several disciplines, including toxicology, psychology, and physiology, have suggested a multifactorial explanatory model for this condition. To guide the clinical evaluation of individuals with this disorder or to respond to requests for epidemiologic investigation, the health care practitioner should be aware of current controversies, including knowledge gaps and the need for further research.


The term multiple-chemical sensitivity was defined in 1987 as 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. These seven criteria should be met:

  1. The disorder is acquired in relation to some documentable environmental exposure(s), insult(s), or illness(es).

  2. Symptoms involve more than one organ system.

  3. Symptoms recur and abate in response to predictable stimuli.

  4. Symptoms are elicited by exposures to ...

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