Polyallergy (Multiple Chemical Sensitivity) is Associated with Excessive Healthcare Utilization, Greater Psychotropic Use, and Greater Mental Health/Functional Somatic Syndrome Disorder Diagnoses: A Large Cohort Retrospective Study.

Background: Associations between the crude capture of polyallergy-also known as multiple chemical sensitivity or multiple drug intolerance syndrome-and mental health/functional somatic syndrome disorders, healthcare utilization, or other clinical phenomenon have not been examined extensively.

Methods: An IRB-approved retrospective chart review of all patients between age 18 and 70 who had a clinical encounter at a large medical center between 2009 and 2014. Patients were stratified into 4 categories based on the absolute number of chart-documented allergies: (1) no allergies; (2) normal allergy (1-4 allergies); (3) polyallergy (5-9 allergies); and (4) "ultrapolyallergy," (≥10 allergies), which were corroborated through a sensitivity analysis. Demographics, comorbidities, and medications were clustered per allergy grouping. Analysis of variance, chi-square, and multivariable logistic regression analyses were employed to test for associations.

Results: 2,007,434 patients were examined ("no allergy" group, n = 1,423,631, 70.9%; "normal allergy" group: n = 549,927, 27.4%; "polyallergy" group n = 29,453, 1.5%; "ultrapolyallergy" group, n = 4,423, 0.22%). Proportion of females increased from 51% in the "no allergy" group to 89.6% in the "ultrapolyallergy" group (p < 0.001). Rates of mental health and functional somatic syndrome disorder diagnoses increased significantly across allergy groups (p < 0.001). All psychotropic medication classes were increased significantly across allergy groups (p < 0.001). Healthcare utilization was also significantly elevated across allergy cohorts (p <0.001).

Conclusions: This study demonstrates that polyallergy/multiple chemical sensitivity may serve as a crude yet meaningful indicator of comorbid psychopathology. Drug intolerance mechanisms are reviewed, and both clinical and investigational implications are examined.