Chemical intolerance: involvement of brain function and networks after exposure to extrinsic stimuli perceived as hazardous

BACKGROUND@#Chemical intolerance (CI) is a chronic condition characterized by recurring and severe symptoms triggered by exposure to low levels of odorous or pungent substances. The etiology of CI has been a controversial subject for a long time. The aim of this review is to summarize findings on the neurological processing of sensory information during and after exposure to low levels of odorous or pungent substances in individuals with CI, focusing on the brain function and networks.@*METHODS@#Scientific studies on CI published between 2000 and 2019 in academic peer-reviewed journals were systematically searched using medical and scientific literature databases. Only peer-reviewed articles reporting original research from experimental human studies directly associated with CI, and involving related neurological responses or brain imaging after exposure to odorous or pungent substances (i.e., in chemical provocation tests), were considered.@*RESULTS@#Forty-seven studies were found to be eligible for a full-text review. Twenty-three studies met the selection criteria and were included in this review. Evidence indicated that differences between subjects with CI and healthy controls were observed by brain imaging during and after exposure to odorous or pungent substances. Differences in brain imaging were also observed between initial exposure and after exposure to these substances. Neurological processing of sensory information after exposure to extrinsic stimuli in the limbic system and related cortices were altered in subjects with CI. A previous documentable exposure event was likely to be involved in this alteration.@*CONCLUSIONS@#This review documents consistent evidence for the altered neurological processing of sensory information in individuals with CI. Further neurophysiological research exploring the processing of extrinsic stimuli and cognition of sensation through the limbic system and related cortices in CI, and the appearance of symptoms in individuals with CI, are required.

Evaluation of subjective symptoms of Japanese patients with multiple chemical sensitivity using QEESI(c)

<p><b>OBJECTIVES</b>The Quick Environment Exposure Sensitivity Inventory (QEESI(c)) has been used as a questionnaire to evaluate subjective symptoms of patients with multiple chemical sensitivity (MCS), also known as idiopathic environmental intolerance, in Japan. However, no cutoff value for Japanese subjects has yet been established. We designed this study to establish a cutoff value for Japanese subjects using QEESI(c) for screening of MCS patients.</p><p><b>METHODS</b>A questionnaire using the QEESI(c) was administered to 103 MCS patients and 309 healthy control subjects matched for age and sex. QEESI(c) scores of the two groups were compared using logistic regression analysis, receiver operating characteristic analysis, and the Mann-Whitney test.</p><p><b>RESULTS</b>Cutoff values for Japanese subjects were determined for the Chemical Intolerance subscale (40), Symptom Severity subscale (20), and Life Impact subscale (10). The subjects whose scores exceeded the cutoff values in any two subscales accounted for 88.4% of the patients but only 14.5% of the controls.</p><p><b>CONCLUSIONS</b>Our results suggest that subjects meeting two out of three subscale criteria can be screened as "patients suffering from a low level of environmental chemicals such as MCS" in Japan.</p>