Multiple chemical sensitivity
Multiple chemical sensitivity (MCS) is an unrecognized and controversial diagnosis characterized by chronic symptoms attributed to exposure to low levels of commonly used chemicals.[1][2] Symptoms are typically vague and non-specific. They may include fatigue, headaches, nausea, and dizziness.
Although these symptoms can be debilitating, the cause is unknown. MCS is not recognized as an organic, chemical-caused illness by the World Health Organization, American Medical Association, or any of several other professional medical organizations.[3] Recent imaging studies have shown that it is likely a neurological condition.[4]
Symptoms[edit]
Symptoms are typically vague and non-specific, such as fatigue or headaches.[12] These symptoms, although they can be disabling, are called non-specific because they are not associated with any single specific medical condition.
Symptoms affect a variety of different organ systems. Different people have different symptoms and different affected systems, but cognitive and neurologic symptoms (e.g., headache and brain fog) are common, as are systemic symptoms (e.g., fatigue).[5] Other people have symptoms affecting the eyes, ears, and nose (e.g., stuffy nose), the respiratory system (e.g., shortness of breath), gastrointestinal system (e.g., nausea), musculoskeletal system (e.g., joint pain), or dermatological system (e.g., itching).[5]
A 2010 review of MCS literature said that the following symptoms, in this order, were the most reported in the condition: headache, fatigue, confusion, depression, shortness of breath, arthralgia, myalgia, nausea, dizziness, memory problems, gastrointestinal symptoms, respiratory symptoms.[12]
Symptoms mainly arise from the autonomic nervous system (such as nausea or dizziness) or have psychiatric or psychological aspects (such as difficulty concentrating).[13]
Diagnosis[edit]
In practice, diagnosis relies entirely upon the self-reported claim that the symptoms are triggered by exposure to various substances.[28] Commonly attributed substances include scented products (e.g. perfumes), pesticides, plastics, synthetic fabrics, smoke, petroleum products, and paint fumes.[1]
Many other tests have been promoted by various people over the years, including testing of the immune system, porphyrin metabolism, provocation-neutralization testing, autoantibodies, the Epstein–Barr virus, testing for evidence of exposure to pesticides or heavy metals, and challenges involving exposure to chemicals, foods, or inhalants.[28] None of these tests correlate with MCS symptoms, and none are useful for diagnosing MCS.[28]
The stress and anxiety experienced by people reporting MCS symptoms are significant.[28] Neuropsychological assessments do not find differences between people reporting MCS symptoms and other people in areas such as verbal learning, memory functioning, or psychomotor performance.[28] Neuropsychological tests are sensitive but not specific, and they identify differences that may be caused by unrelated medical, neurological, or neuropsychological conditions.[28]
Another major goal for diagnostic work is to identify and treat any other medical conditions the person may have.[28] People reporting MCS-like symptoms may have other health issues, ranging from common conditions, such as depression or asthma, to less common circumstances, such a documented chemical exposure during a work accident.[28] These other conditions may or may not have any relationship to MCS symptoms, but they should be diagnosed and treated appropriately, whenever the patient history, physical examination, or routine medical tests indicates their presence.[28] The differential diagnosis list includes solvent exposure, occupational asthma, and allergies.[28]
Management[edit]
There is no single proven treatment for MCS.[15] The goal of treatment is to improve quality of life, with fewer distressing symptoms and the ability to maintain employment and social relationships, rather than to produce a permanent cure.[28]
A multidisciplinary treatment approach is recommended.[27] It should take into account the uncommon personality traits often seen in affected individuals and physiological abnormalities in sensory pathways and the limbic system.[27] There is also no scientific consensus on supportive therapies for MCS, "but the literature agrees on the need for patients with MCS to avoid the specific substances that trigger reactions for them and also on the avoidance of xenobiotics in general, to prevent further sensitization."[15]: 17 [12]
Common self-care strategies include avoiding exposure to known triggers and emotional self-care.[28] Healthcare providers can provide useful education on the body's natural ability to eliminate and excrete toxins on its own and support positive self-care efforts.[28] Avoiding triggers, such as by removing smelly cleaning products from the home, can reduce symptoms and increase the person's sense of being able to reclaim a reasonably normal life.[28] However, for other people with MCS, their efforts to avoid suspected triggers will backfire, and instead produce harmful emotional side effects that interfere with the overall goal of reducing distress and disability.[28] Treatments that have not been scientifically validated, such as "elimination or rotary diversified diets", hormone supplement and chemical detoxification through exercise have been used by people with MCS. "Controversial treatment methods offer hope of improvement to many individuals with MCS.[28]" Unproven treatments can be expensive, may cause side effects, and may be counterproductive.[28]
Various combinations of different antioxidants together with “detoxifying” measures that are not evidence based are recommended by some authors. “Treatment with a multitude of pills and infusions may lead to “catastrophizing”, thus making patients perceive their disorder particularly negatively; this phenomenon is known to have a negative impact on the subsequent disease course ... such treatments place a significant financial strain on patients.”[29]
History[edit]
MCS was first proposed as a distinct disease by Theron G. Randolph in 1950. In 1965, Randolph founded the Society for Clinical Ecology as an organization to promote his ideas about symptoms reported by his patients. As a consequence of his insistence upon his own, non-standard definition of allergy and his unusual theories about how the immune system and toxins affect people, the ideas he promoted were widely rejected, and clinical ecology emerged as a non-recognized medical specialty.[28]
Since the 1950s, many hypotheses have been advanced for the science surrounding multiple chemical sensitivity.[14]
In the 1990s, an association was noted with chronic fatigue syndrome, fibromyalgia, and Gulf War syndrome.[40]
In 1994, the AMA, American Lung Association, US EPA and the US Consumer Product Safety Commission published a booklet on indoor air pollution that discusses MCS, among other issues. The booklet further states that a pathogenesis of MCS has not been definitively proven, and that symptoms that have been self-diagnosed by a patient as related to MCS could actually be related to allergies or have a psychological basis, and recommends that physicians should counsel patients seeking relief from their symptoms that they may benefit from consultation with specialists in these fields.[41]
In 1995, an Interagency Workgroup on Multiple Chemical Sensitivity was formed under the supervision of the Environmental Health Policy Committee within the United States Department of Health and Human Services to examine the body of research that had been conducted on MCS to that date. The work group included representatives from the Centers for Disease Control and Prevention, United States Environmental Protection Agency, United States Department of Energy, Agency for Toxic Substances and Disease Registry, and the National Institutes of Health. The Predecisional Draft document generated by the workgroup in 1998 recommended additional research in the basic epidemiology of MCS, the performance of case-comparison and challenge studies, and the development of a case definition for MCS. However, the workgroup also concluded that it was unlikely that MCS would receive extensive financial resources from federal agencies because of budgetary constraints and the allocation of funds to other, extensively overlapping syndromes with unknown cause, such as chronic fatigue syndrome, fibromyalgia, and Gulf War syndrome. The Environmental Health Policy Committee is currently inactive, and the workgroup document has not been finalized.[42]
The different understandings of MCS over the years have also resulted in different proposals for names.[9] For example, in 1996 the International Programme on Chemical Safety proposed calling it idiopathic environmental illness, because of their belief that chemical exposure may not the sole cause,[7] while another researcher, whose definition includes people with allergies and acute poisoning, calls it chemical sensitivity.[9]