Idiopathic Environmental Intolerance May Have Psychological Component

February 18, 2000

New York (MedscapeWire) Feb 18 — A study by Canadian researchers in the February issue of the Journal of Allergy and Clinical Immunology suggests that patients with idiopathic environmental intolerance (IEI, formerly known as multiple chemical sensitivity) display high anxiety sensitivity similar to patients with panic disorder (PD) under controlled conditions.

Previous studies have been unable to prove any underlying allergic or toxic basis to IEI. Other research has found that IEI has increased psychiatric morbidity and shares many features with PD which involve the onset of sudden anxiety. Symptoms shared include chest tightness, breathlessness, palpitations, apprehension, and avoidance of situations where symptoms occur.

In this blinded study, patients inhaled differing concentration of oxygen and CO 2 through a flow spirometer. After each inhalation, patients were asked to rate each panic symptom and their sensations of panic and fear on an objective Diagnostic Symptom Questionnaire.

When inhaling increasing concentrations of CO 2, a large percentage (48%-92%) of patients with PD frequently experienced panic symptoms, whereas only 5% of healthy subjects noted similar symptoms. Researchers found that 71% of IEI patients fulfilled similar PD criteria after inhaling CO 2. There were no significant differences between IEI and control groups in terms of actual breathing rate, heart rate, and other physical measures.

Investigators concluded that the high rate of anxiety response to inhaled CO 2 among IEI patients shows a tendency to overreport and possibly catastrophically misinterpret benign physical symptoms, a consistent finding among patients with PD. The authors suggest a psychological assessment should be considered in all patients with IEI.

J Allergy Clin Immunol. 2000;105(2):358-363

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