Abstract

Whereas most idiosyncratic environmental sensitivity complaints do not fit known diagnoses, the multiple chemical sensitivities syndrome (MCS) is an extreme presentation that has defined diagnostic criteria. MCS symptomatics claim that they acquired a sensitized state as the result of a chemical exposure, usually to a solvent or pesticide, but not to a fragrance. Before this exposure, they did not experience symptoms. Following sensitization, symptoms increasing in number and severity with time are attributed by the MCS symptomatic to various exposures that are innocuous to most individuals. Although phenomenological studies have provided no evidence that particular odors elicit MCS symptoms, low levels of fragrances and perfumes are frequently associated with the reporting of MCS symptoms. This evaluation examines proposed mechanisms by which odorants and fragrances might cause either sensitization or elicitation of MCS symptoms, including altered odor sensitivity, primary irritancy or irritancy-induced upper airway reactivity, neurogenic switching of trigeminal irritancy signals, time-dependent sensitization and limbic kindling, CNS toxicity, and various psychiatric conditions. In no case was there persuasive evidence that any olfactory mechanism involving fragrance underlies either induction of a sensitized state or the triggering of MCS symptoms. Fragrances and other odorants could, however, be associated with symptoms as claimed by MCS symptomatics, because they are recognizable stimuli, but fragrance has not been demonstrated to be causal in the usual sense.

Author Keywords: environmental illness; models, biological; models, psychological; multiple chemical sensitivity; odors; perfume; smell.

*1 The authors acknowledge Mark R. Cullen of the Yale Occupational and Environmental Medicine Clinic and Howard M. Kipen of the Environmental and Occupational Health Sciences Institute at the State University of New Jersey for reviewing a draft of the manuscript and providing their valuable comments. Also, the authors are grateful to Janet Marino and Melissa Mohan for their assistance in preparing the manuscript.

*2 Funding for this study came from unrestricted contributions that support the activities of the Environmental Health and Safety Council and the Toxicology and Risk Assessment Program, some of which was provided by the chemical, pharmaceutical, and fragrance industries.

*3 Cullen, M, R

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