Multiple chemical sensitivity (MCS) is a highly controversial disorder associated with unusually extreme sensitivity or allergy-like reaction in response to low-level exposure to chemicals, solvents, petroleum products, smoke, pollen, pet fur, perfumes, and volatile organic chemicals (VOCs) in particular. The disorder is also referred to as multiple chemical sensitivity syndrome, chemical injury, chemical sensitivity, environmental illness, multiple allergy, and total allergy syndrome, along with many other related terms.
Unlike true allergies, MCS does not have an underlying cause that is relatively well understood. Consequently, it is generally regarded as idiopathic—meaning that it does not have a known mechanism of causation. As of 2012, MCS is not recognized as an “established organic disease” by the American Medical Association, the American Academy of Allergy and Immunology, the American College of Physicians, the International Society of Regulatory Toxicology and Pharmacology, and many other medical organizations.
In 1987, Dr. Mark R. Cullen defined MCS within the paper “The Worker with Multiple Chemical Sensitivities: An Overview” (2:655–661) within the journal Occupational Medicine. Cullen's definition states that MCS is a disorder:
In 2005, Dr. Michael Lacour and colleagues expanded the definition made by Cullen within the article “Multiple Chemical Sensitivity Syndrome (MCS)—Suggestions for an Extension of the U.S. MCS-case” (208, 141–151) in the journal International Journal of Hygiene and Environmental Medicine. Lacour includes these six fundamentals for MCS: (1) it is a chronic condition, (2) its symptoms recur reproducibly, (3) it occurs in multiple organ systems, (4) it occurs in response to low levels of exposure, (5) it occurs because of multiple unrelated chemicals, and (6) it improves or is resolved when incitants are removed. Lacour also adds the following symptoms:
MSC has been cited to occur due to a multitude of chemicals. Some of the more common include:
MCS has no uniform cause or consistent, measurable features. Insufficient medical evidence has yet to confirm a relationship between any of the various possible causes of MCS and the symptoms that individuals report. Individuals who have been diagnosed with MCS report widely varied symptoms. This makes it very difficult for MCS to be treated. Further, medical professionals contend it is a chronic condition identified by increased sensitivity to even slight exposure to chemicals, and that multiple symptoms occur in multiple organ systems. An episode of MCS is often caused by exposure to a newly introduced consumer product, such as new carpet. Proposed theories regarding the cause of MCS usually center around allergies, immune system dysfunction, neurobiological sensitization, and various psychological theories.
People with MCS often experience some of the following symptoms:
Sometimes these symptoms are so disabled that the person cannot live or work except in an environment completely devoid of chemicals.
Critics argue that this condition should not receive clinical recognition as a disease, insisting that there is no conclusive scientific evidence to link the causes to the symptoms of the condition.
Cases of MCS are usually diagnosed and evaluated based on the patient's description of symptoms and their connection to environmental exposures. Although it is clear that some people are very sensitive to various microorganisms, noxious chemicals, and common foods, there is little evidence that an immunologic basis exists for generalized allergy to environmental substances.
A medical professional will usually diagnosis MCS when observing all of the following:
Because MCS is not recognized as a valid medical condition, little has been done with respect to a public response. The medical community treats MCS as best as it can under these limited circumstances.
For the most part, the prognosis for sufferers of MCS is best when they avoid pollutants and toxicants.
One can prevent MCS by avoiding all chemicals that are known to adversely affect one's health. Although difficult at best, it is advised to live in an environment that is absent of pollutants and irritants of any kind—that is, a chemical-free environment.
See also Toxicology ; Volatile organic compound .
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William A. Atkins, BB, BS, MBA