Multiple chemical sensitivity: a review of its pathophysiology

Abstract

Multiple chemical sensitivity (MCS) is an unexplained acquired medical condition that includes multiple, vague, recurrent, and non-specific symptoms in different organs. They are attributed to exposures to various and structurally unrelated environmental chemicals at concentration levels that are well tolerated by the majority of people and normally considered not to have toxic effects in humans. The aim of this review is to examine the multiple explanatory hypotheses for the pathophysiology of MCS: genetic, metabolic, neurological, immunological, and psychological. Several publications suggest a neurological and immunological activation. However, this neurological and immunological hyperresponse is not always observed when performing challenge tests. This suggests that behavioral conditioning could be an important mechanism in the pathogenesis of MCS. Even if psychiatric conditions appear not to be a major cause of MCS, in the case of genuine psychiatric disease, psychotherapeutic therapy is mandatory. Because of the complexity of the pathophysiology, there is no specific drug to treat MCS. However, the use of cognitive behavioral therapy is encouraged, as it has a significant positive impact on patients’ perception of their illness.