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Idiopathic Environmental Intolerance

(Multiple Chemical Sensitivity; Environmental Illness)


Donald W. Black

, MD, University of Iowa, Roy J. and Lucille A. Carver College of Medicine

Reviewed/Revised Mar 2022 | Modified Dec 2023

Idiopathic environmental intolerance involves a wide variety of intermittent symptoms that seem to be triggered by exposure to low levels of several identifiable or unidentifiable substances commonly present in the environment or sometimes to electromagnetic fields.

  • Symptoms may include rapid heart rate, chest pain, sweating, shortness of breath, fatigue, flushing, and dizziness.

  • Tests may be done to rule out allergic disorders as causes of the symptoms.

  • Treatment may involve psychotherapy, avoidance of certain substances, or both.

Idiopathic environmental intolerance is usually defined as the development of multiple symptoms that people who have them believe are caused by exposure to any number of identifiable or unidentifiable chemical substances (inhaled, touched, or ingested) or exposure to electromagnetic fields in a person who has no detectable organ dysfunction or related physical abnormalities.

Symptoms do not always occur after a person is exposed to a substance, even at levels higher than those that previously seemed to cause symptoms. Also, blood tests do not consistently show activation of the person's immune system. Thus, some doctors consider idiopathic environmental intolerance to have a psychologic cause, probably a type of somatic symptom disorder Somatic Symptom Disorder Somatic symptom disorder is characterized by one or more chronic physical symptoms accompanied by significant and out-of-proportion levels of distress, worries, and difficulty in daily functioning... read more or an anxiety disorder similar to agoraphobia Agoraphobia Agoraphobia is fear or anxiety about being in situations or places (for example, in crowds and shopping malls or while driving) with no way to escape easily or in which help might not be available... read more (fear of going out in public) or a panic attack Panic Attacks and Panic Disorder A panic attack is a brief period of extreme distress, anxiety, or fear that begins suddenly and is accompanied by physical and/or emotional symptoms. Panic disorder involves recurrent panic... read more . Others do believe the disorder may be a type of allergic reaction Allergic Reactions and Other Hypersensitivity Disorders because some people do have various changes in their immune system although this is rare). However, there is no consistent pattern of such changes among people who have this syndrome, and the cause remains unknown.


Some people with idiopathic environmental intolerance start having symptoms after a single exposure to high levels of various toxic substances. People may attribute their symptoms to exposure to these substances, but evidence is usually lacking.

Symptoms may include a rapid heart rate, chest pain, sweating, shortness of breath, fatigue, flushing, dizziness, nausea, choking, trembling, numbness, coughing, hoarseness, and difficulty concentrating.

Commonly reported triggers for idiopathic environmental intolerance include

  • Alcohol and drugs

  • Caffeine and food additives

  • Carpet and furniture odors

  • Fuel odors and engine exhaust

  • Painting materials

  • Perfume and other scented products

  • Pesticides and herbicides

  • Mobile telecommunication devices


The diagnosis of idiopathic environmental intolerance is suspected if the symptoms

  • Recur after repeated exposure to the chemical substance

  • Recur after exposure to levels much lower than those that have been tolerated previously or that are commonly tolerated by others

  • Subside when the person leaves the offending environment

  • Develop in response to a wide variety of unrelated chemical substances

If a person's symptoms suggest idiopathic environmental intolerance, doctors try to identify possible causes of the symptoms, including other disorders. For example, symptoms could be caused by building-related illnesses Building-Related Illnesses Building-related illnesses are disorders that affect the lungs as well as other parts of the body and are caused by exposure to substances within buildings. Building-related illnesses generally... read more , allergic disorders, some autoimmune disorders, or psychologic disorders. Depending on the person's symptoms and the findings during the physical examination, additional tests or assessments may be helpful. For example, blood and skin prick tests may be done to diagnose allergic disorders, or, if depression or anxiety seems possible, evaluation by a psychiatrist may help.


  • Avoidance of suspected triggers

  • Sometimes psychotherapy

People with idiopathic environmental intolerance may try avoiding the toxic substances thought to cause their symptoms. However, avoidance may be difficult because many of these substances are widespread. Also, the substances being avoided may not be the true cause of symptoms, so avoidance may be ineffective. People should avoid too much social isolation. Psychotherapy can sometimes be helpful. The aim of psychotherapy is not to convince people that the cause of idiopathic environmental intolerance is psychologic. The aim, rather, is to enable people to cope with their symptoms and improve their quality of life.

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