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Idiopathic environmental intolerances (IEI) are medicalsyndromes with no proven cause, but which the affected people attribute to various environmental situations.[1] The most common forms aremultiple chemical sensitivity,electromagnetic hypersensitivity (electricity), andwind turbine syndrome (noise).[1]
Although the identifiedenvironmental factor differs, there are several qualities shared by all of these conditions. All of them are controversial, and none of them result from a scientifically provenpathogenesis andpathophysiology.[1]
There is a wide variety of symptoms, with no pattern associating particular exposures with particular symptoms.[1] Symptoms do not appear consistently after exposure inblinded experiments.[1] However, the expectancy-inducednocebo effect seems to produce symptoms when they believe they have been exposed, even if they have not been exposed to it.[1] That is, people generally do not feel bad when they believe they are safe, but they may learn to fear exposure to a particular substance or situation, if something unrelated but unpleasant happens at the same time.[1]
Evidence indicates that at least part of the distress has a psychological or behavioral component.[1] For example, people with IEIs are oftenhypervigilant about how their bodies feel.[1] One medical challenge relates to themind–body problem, with people's experiences being dismissed as "all in their heads" and debates about whether it is a "real" or "physical" condition.[1]
It can be difficult to distinguish IEIs from othersomatic symptom disorders and from poorly understood syndromes, such asmyalgic encephalomyelitis/chronic fatigue syndrome andfibromyalgia.[1]
Multiple chemical sensitivity (MCS) is achronic condition involvingnon-specific physical and psychological symptoms that appear when the affected person has been exposed to "chemicals", or at least believes they have been exposed to.[1] Typical triggers include substances with strong or bad odors, such asvehicle exhaust,smoke, orcleaning products.[1] Symptoms often relate to thecentral nervous system (e.g., difficulty concentrating, feelinglightheaded),musculoskeletal system (e.g., pain),gastrointestinal system (e.g., indigestion), andskin (e.g., rash), but anyorgan system can be affected.[1] Emotional and mood-related symptoms are common (e.g., feeling anxious after a perceived exposure).[1] They are less likely to attribute their symptoms to psychological factors than healthier people.[1] For example, a healthier person might say that a headache was probably caused by stress, but a person with MCS is more likely to blame an external factor, such as chemicals.
People with MCS frequently have other medical conditions, includingsomatic symptom disorder,affective disorder,anxiety disorder, andpsychotic disorders.[1] They are oftenneurotic, have highnegative affectivity (e.g., feeling anxious), and tend to beabsorbed by perceived exposures.[1] They also tend to have very strong concerns about chemicals and pollution.[1]
Electromagnetic hypersensitivity (EHS or IEI-EMF) is a chronic condition very similar to MCS, except that the affected person blameselectromagnetic fields for their symptoms, rather than chemicals.[1] Typical claims for triggers involve mobile phones andcell sites,cordless telephones, andpower lines.[1] Symptoms produced involvesleep disorders,headaches,nervousness,fatigue, and difficulty with concentrating.[1]
People with EHS frequently have other mental disorders, such asmajor depressive disorder,generalized anxiety disorder, andsomatic symptom disorder.[1]
Infrasound hypersensitivity (IHS) is a collection of symptoms that appears when the person has been exposed to low-frequency orinfrasound noise, usually from machinery such as awind turbine.[1] It is sometimes calledwind turbine syndrome orvibroacoustic syndrome.[1] The trigger for this is the noise produced, and not, e.g., disliking the visual appearance of wind turbines. Symptoms include ear-related symptoms (e.g.,tinnitus), balance problems (e.g.,dizziness), problems with concentration and memory,heart palpitations, fatigue, and sleep problems.[1] The psychological symptoms, which can be significant, include feelings of frustration, anger, depression, and anxiety.[1] Feeling annoyed by the presence of wind turbines is correlated with poor sleep.[1]
IHS is not the same ashyperacusis.[1]
Other IEIs includesick building syndrome and some types offood intolerance.[1]