Concomitant positive reactions to allergens in a patch testing standard series from 1988–1997

image Patch testing is a useful diagnostic technique in patients with suspected allergic contact dermatitis (ACD). Concomitant reactions may reflect associations between tested allergens. image This study was performed to identify positive correlations between reactions to test substances in a standard screening series. The results of patch testing in patients seen from 1988 to 1997 are described. image Data were collected from chart review for patients who underwent patch testing to the full standard screening series at the Massachusetts General Hospital Contact Dermatitis Clinic. The Fisher exact test was used to evaluate associations between allergens. image A total of 927 patients were patch tested to 22 allergens included in a screening tray. The mean age was 43.9 years, and 68.6% were women. Two or more positive reactions occurred in 36.5% of patients. Reactions to 13 pairs of allergens were found to be significantly correlated: balsam of Peru/fragrance mix, carba mix/thiuram mix, carba mix/paraben mix, cobalt chloride/potassium dichromate, cobalt chloride/nickel sulfate, ethylenediamine/neomycin sulfate, formaldehyde/imidazolidinyl urea, formaldehyde/paraben mix, formaldehyde/quaternium-15, imidazolidinyl urea/quaternium-15, neomycin sulfate/potassium dichromate, paraben mix/quaternium-15, and potassium dichromate/thimerosal. image Concomitant reactions to 13 pairs of allergens in a standard series occurred at a rate greater than would be predicted by chance. Such associations may reflect cross-sensitization or cosensitization.