Identification of causative chemicals of allergic contact dermatitis using a combination of patch testing in patients and chemical analysis. Application to cases from rubber footwear.

5 cases of allergic contact dermatitis from rubber footwear were investigated by a combination of patch testing in patients and chemical analysis of causative rubber products. Our studies revealed 2-mercaptobenzothiazole (MBT) and benzothiazyl disulfide (MBTS) (typical allergenic accelerators) as causative chemicals in 3 cases from children's rubber shoes, ladies' rubber boots and ladies' canvas shoes. These 3 patients reacted to mercaptobenzothiazole-type accelerators including MBT and MBTS. MBT and MBTS were determined in each item of causative footwear by chemical analysis, including extraction by shaking with acetone-chloroform (1:1) mixture at room temperature and determination using reversed-phase high-performance liquid chromatography (RP-HPLC). Subsequently, we identified styrenated phenol (SP), a newly found allergenic antioxidant, as a causative chemical in a case from ladies' canvas shoes. The patient reacted to SP but not to MBT and MBTS, though SP, MBT and MBTS were determined in the causative shoes by gas chromatography (GC), GC-mass spectrometry (GC-MS) and HPLC. We also identified p-tert-butylphenol-formaldehyde resin (PTBP-F-R), (a known allergenic adhesive ingredient) as a causative chemical in a case from ladies' sneakers. The patient reacted to PTBP-F-R but not to p-tert-butylphenol (PTBP), MBT and MBTS. These 4 compounds were determined in the causative sneakers by GC, GC-MS and HPLC. Thus, our studies revealed that not only known allergens, such as MBT, MBTS and PTBP-F-R, but also a newly found one, such as SP, were important causes of allergic contact dermatitis from rubber footwear.