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Multiple chemical sensitivity syndrome
Last reviewed: 05.07.2025
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Multiple chemical sensitivity syndrome (idiopathic environmental intolerance) is characterized by ongoing, vague symptoms attributed to exposure to low-level, chemically unrelated substances commonly found in the environment. Symptoms are numerous and often involve a wide organ system, but physical findings are subtle. Diagnosis is by exclusion. Treatment is psychological support and avoidance of perceived irritants, although these irritants are rarely identified.
[ What causes multiple chemical sensitivity syndrome?
There is no universally accepted definition, but multiple chemical sensitivity syndrome is generally defined as the development of multiple symptoms attributed to exposure to any number of identifiable or unidentifiable chemicals (ingested through inhalation, touch, or ingestion) in the absence of clinically detectable organ dysfunction or associated physical signs.
Many immunological and nonimmunological theories have been proposed. All of these theories are hampered by the lack of a consistent dose-response relationship to the proposed causative substances; that is, the symptoms cannot be reproduced after exposure to high levels of a substance that was previously thought to have caused the reaction at much lower levels. Similarly, consistent objective evidence of systemic inflammation, cytokine excess, or immune activation in response to the symptoms is clearly lacking. Many clinicians believe the etiology to be psychological—perhaps a form of somatization disorder. Others suggest that the syndrome is a type of panic attack or agoraphobia. Some aspects of the syndrome resemble the no longer used psychological diagnosis of neurasthenia.
Although measurable biological abnormalities (eg, decreased B-cell levels, elevated immunoglobulin E levels) are rare, some patients do have such abnormalities. However, these abnormalities appear in an inconsistent pattern, and their significance remains uncertain.
Symptoms of Multiple Chemical Sensitivity Syndrome
Symptoms (e.g., tachycardia, chest pain, sweating, shortness of breath, fatigue, flushed face, dizziness, nausea, choking, tremors, numbness, cough, hoarseness, inability to concentrate) are numerous and usually involve more than one organ system. Most patients are given a long list of suspected substances, either self-identified or identified by a physician during a previous evaluation. Such patients often go to great lengths to avoid these substances in the future: changing residence and work, avoiding all foods containing the "chemicals," sometimes wearing masks in public or staying away from public places altogether. Physical examination is largely inconclusive.
Diagnosis of multiple chemical sensitivity syndrome
Diagnosis initially involves exclusion of obvious allergies and other known disorders with similar characteristics (eg, atopic disorders such as asthma, allergic rhinitis, food allergies, and angioedema). Atopic disorders are excluded based on a typical clinical history, skin prick tests, specific immunoglobulin E serologic testing, or all three. Consultation with an allergist may be necessary.
Treatment of multiple chemical sensitivity syndrome
Despite the uncertain relationship between cause and effect, treatment is usually aimed at avoiding the suspected precipitating agents, which can be difficult given that many of them are ubiquitous. However, social isolation and expensive and highly debilitating measures aimed at avoiding possible causes of the disease must be discouraged. Psychological assessment and intervention can help, but many patients resist this. However, the point of this approach is not to demonstrate that the cause is psychological, but rather to help patients cope with their illness.