Chemical sensitivity: symptom, syndrome or mechanism for disease?

• Published in: Toxicology (Amsterdam) 1996-07, Vol.111 (1), p.69-86
• Main Author: Miller, Claudia S.
• Format: Article
• Language: English
• Subjects: Chemical sensitivity; Disease Susceptibility; Environmental etiology; Environmental exposure; Humans; Multiple Chemical Sensitivity - etiology; Multiple Chemical Sensitivity - physiopathology; Syndrome; Theory for disease; Toxicant-induced loss of tolerance
• ISSN: 0300-483X; 1879-3185
• DOI: 10.1016/0300-483X(96)03393-8

Several different meanings have been attached to the term “chemical sensitivity” by those who use it. Feeling ill from odors is a symptom reported by approximately one-third of the population. The syndrome of chemical sensitivity, frequently called “Multiple Chemical Sensitivity” or “MCS” has been the subject of three federallysponsored workshops; at least five different case definitions for research on MCS have been proposed. In contrast, the hypothesis that chemical sensitivity may be a mechanism for disease posits that a broad spectrum of “recognized” chronic illnesses, ranging from asthma and migraine to depression and chronic fatigue, may be the consequence of environmental chemical exposures. According to this theory, a two-step process occurs: (1) an initial salient exposure event(s) (for example, a one-time, intermittent, or continuous exposure to pesticides, solvents, or air contaminants in a sick building) interacts with a susceptible individual, causing loss of tolerance for everyday, low level chemical inhalants (car exhaust, fragrances, cleaning agents), as well as for foods, drugs, alcohol, and caffeine; (2) thereafter, such common, formerly well-tolerated substances trigger symptoms, thus perpetuating illness. “Masking” (acclimatization, apposition, and addiction) may hide these exposure-symptom relationships, thus obfuscating the environmental etiology of the illness. Accumulating clinical observations lend credence to a view of chemical sensitivity as an emerging theory of disease causation and underscore the need for its testing in a rational, scientific manner. While chemical sensitivity may be the consequence of chemical exposure, the term “toxicant-induced loss of tolerance” more fully describes the two-step process under scrutiny.