Multiple chemical sensitivity
The syndrome of multiple chemical sensitivities, also known as environmental intolerances, is a poorly understood and often disputed syndrome. Several clinicians are reporting an increase in the number of persons who develop sensitivities to extraordinarily low levels of environmental chemicals. The contrast between the intensity of the reactions and the concentrations of the substances triggering those reactions is acute, which led several commentators to speculate that MCS had a strong psychogenic component. MCS remains a disabling condition, and, for many researchers, in Kuhn's terms, a compelling anomaly.[1]
Description
| The 6 criteria of multiple chemical sensitivities
1. The symptoms are reproducible with repeated chemical exposure; 2. The condition is chronic; 3. Low levels of exposure (lower than previously tolerated) result in manifestations of the syndrome; 4. The symptoms improve or resolve when the incitants are removed; 5. Responses occur to multiple chemically unrelated substances; and 6. Symptoms involve multiple organ systems.[2] |
Epidemiology
(in progress)
Genetic basis
People diagnosed using the 1999 consensus statement criteria[2] have significant differences in some drug-metabolizing enzymes and other enzymes involved in detoxication.[3] These findings, which require replication, point to an unequivocal somatic and toxic basis to multiple chemical sensitivities.
Immunological basis
In a case control study involving 417 persons (223 cases, 194 controls), lymphocyte count was found to be consistent low in victims of MCS.[4]
The TILT theory of environmental diseases
Claudia Miller of the University of Texas points out that the term multiple chemical sensitivity erroneously suggests that the MCS patient is only intolerant to so-called "chemicals", while the evidence rather suggests that people with MCS react as well to very low levels of common food ingredients, such as xanthines and, for example, alcohol.
The Toxicant-Induced Loss of Tolerance (TILT) model describes more closely MCS by specifying that, in this syndrome, there is a generalized loss of tolerance to many unrelated and otherwise benign molecules, and that this loss of tolerance is indeed due to an exposure to toxics (or "toxicants").[5]
References
- ↑ Miller CS (2001). "The compelling anomaly of chemical intolerance". Ann. N. Y. Acad. Sci. 933: 1–23. PMID 12000012. [e]
- ↑ 2.0 2.1 (1999) "Multiple chemical sensitivity: a 1999 consensus". Arch. Environ. Health 54 (3): 147–9. PMID 10444033. [e]
- ↑ McKeown-Eyssen G, Baines C, Cole DE, et al (2004). "Case-control study of genotypes in multiple chemical sensitivity: CYP2D6, NAT1, NAT2, PON1, PON2 and MTHFR". International journal of epidemiology 33 (5): 971–8. DOI:10.1093/ije/dyh251. PMID 15256524. Research Blogging.
- ↑ Baines CJ, McKeown-Eyssen GE, Riley N, et al (2004). "Case-control study of multiple chemical sensitivity, comparing haematology, biochemistry, vitamins and serum volatile organic compound measures". Occupational medicine (Oxford, England) 54 (6): 408–18. DOI:10.1093/occmed/kqh083. PMID 15347780. Research Blogging.
- ↑ Miller CS (1997). "Toxicant-induced loss of tolerance--an emerging theory of disease?". Environ. Health Perspect. 105 Suppl 2: 445–53. PMID 9167978. [e]