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Idiopathic environment intolerance has been labeled in a variety of ways over time.Clinical ecology, the original term, was replaced by the term multiple chemical sensitivity (MCS). Most recently, it has been replaced by idiopathic environmental intolerance which reflects the uncertain nature of the condition and its relationship to chemical exposure. Symptoms are recurrent and nonspecific referable to multiple organ systems such as the central nervous system that the sufferers believe are provoked by exposure to low levels of chemical, biologic or physical agents. The most common environmental exposures include perfumes and scented products, pesticides, domestic and industrial solvents, new carpets, car exhaust, gasoline and diesel fumes, urban air pollution, cigarette smoke, plastics and formaldehyde. Certain foods, food additives, drugs, electromagnetic fields, and mercury in dental fillings have also been reported as triggering events. However symptoms do not bear any relationship to established toxic effects of the specific chemical and occur at concentrations far below those expected to elicit toxicity.

Reported symptoms are markedly variable, but symptoms generally involve either the central nervous system, respiratory and mucosal irritation, or gastrointestinal symptoms. Symptoms may include fatigue, difficulty in concentrating, depressed mood, memory loss, weakness, dizziness, headaches, heat intolerance and arthralgia. In contrast to the frequently debilitating symptomatology, no specific and consistent abnormalities are noted on laboratory or other diagnostic testing. In addition to multiple chemical sensitivity, other terms used to describe idiopathic environmental intolerance include universal allergy, 20^th century disease or cerebral allergy. Other primarily subjectively defined disorders have symptoms that overlap with idiopathic environmental intolerance including chronic fatigue syndrome, sick building syndrome, fibromyalgia, irritable bowel syndrome, and Gulf War syndrome. Intestinal dysbiosis is a diagnosis that could be considered within the category of idiopathic environmental intolerance. Refer to the Fecal Analysis in the Diagnosis of Intestinal Dysbiosis medical policy.

The variable nature of the reported symptoms and the lack of recognized pathologic abnormalities make it extremely difficult to establish objective criteria for the condition, which further hinders research into both the causes and appropriate treatment. One of the commonly quoted conceptual definitions, proposed by Cullen in 1987 includes the following elements:

• The syndrome is acquired after a documentable environmental exposure that may have caused objective evidence of health effects.
• Symptoms are referable to multiple organ systems and vary predictably in response to environmental stimuli.
• The symptoms occur in relation to measurable levels of chemical, but the levels are below those known to harm health.
• No objective evidence of organ damage can be found.

Various causes for idiopathic environmental intolerances have been proposed. An unrecognized form of allergy or immunologic hypersensitivity is a commonly proposed cause. Advocates of this etiology may recommend a large series of immunologic test, including a variety of provocation-neutralization test and a panel of immunologic tests, including immune function test and levels of lymphocyte subsets (i.e., natural killer cells, CD8 cells). Proposed therapies have included avoidance of exposure, either in the environment or in the diet. IVIg may be recommended for injection or sublingual drops of “neutralizing” chemical and food extracts. Others have proposed that exposure to toxic substances may have prompted the immunologic abnormality and, based on this theory, testing of levels of environmental in the blood, urine, or fat may be suggested. Detailed nutritional analyses have also been performed, including levels of trace minerals in the blood, urine or intracellular levels. Intracellular Analysis (FIA) is a series of laboratory tests offered by SpectraCell Labs that measure the intracellular levels of micronutrients, such as vitamins, minerals, and antioxidants in lymphocytes.

It has been proposed that idiopathic environmental intolerance is a manifestation of a psychiatric disease or personality disorder. Studies supporting this cause may include brain-imaging (including PET scans) or psychologic/psychiatric interviews. In some instances, symptoms may appear to coincide after exposure to a viral illness (particularly common with chronic fatigue syndrome); supporters of this theory may recommend a wide variety of tests to detect antibodies or antigens of various viruses. Finally, some have suggested that hypersentivity to Candida may present with a similar array of subjective complaints, and thus recommend testing for Candida in the stool or urine.

It should be noted that some environmentally causes illnesses can be well characterized by their clinical presentation and laboratory tests. For example, in certain instances “sick building” syndrome can be traced back to exposure of microorganisms related to air-handling symptoms. However, in contrast to idiopathic environmental intolerances, these patients experience a limited range of symptoms, and they occur in the affected building only.

Nutritional assessments, including intracellular analysis of micronutrients, are considered investigational in both asymptomatic persons and patients with symptoms suggestive of idiopathic environmental intolerance.

Treatment of idiopathic environmental intolerance with IVIg, neutralizing therapy of chemical and food extracts, avoidance therapy, elimination diets, and oral nystatin (to treat Candida) is considered investigational.

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The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.

1/8/2009: Policy reviewed, no changes

06/07/2010:  Policy description updated regarding symptoms; added link to the Fecal Analysis in the Diagnosis of Intestinal Dysbiosis medical policy. For clarification and consistency purposes, "environmental illness" was changed to "environmental intolerance" throughout the policy. Intent of policy statements unchanged.

07/29/2011: Policy reviewed; no changes.

06/06/2012: Policy reviewed; no changes.

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