What is "multiple chemical sensitivity"

n. (context medicine English) a chronic disease caused by a person's inability to tolerate a variety of environmental substances

Multiple chemical sensitivity (MCS) or idiopathic environmental intolerances (IEI) is a chronic medical condition and syndrome characterized by symptoms that the affected person attributes to low-level chemical exposures to commonly used chemicals. Commonly attributed substances include scented products, pesticides, plastics, synthetic fabrics, smoke, petroleum products, and paint fumes. Symptoms are subjective and vague. Symptoms are also non-specific, meaning that they are common symptoms, such as fatigue or headaches, that are present in hundreds of other illnesses. Commonly reported symptoms also include nausea, dizziness, and inflammation of skin, joints, gastrointestinal tract and airways.

Although the symptoms themselves are real, and can be disabling, 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. Blinded clinical trials have shown MCS patients react as often and as strongly to placebos as they do to chemical stimuli; the existence and severity of symptoms is related to perception that a chemical stimulus is present. Depression, anxiety, somatoform disorder, and similar mental health conditions are commonly associated with reports of MCS.

Prior to the mid-1980s, when the term "multiple chemical sensitivity" was coined, the syndrome went by such names as universal allergy, 20th-century disease, chemical hypersensitivity syndrome, total allergy syndrome, and cerebral allergy.