Isolation, via activity-directed fractionation, of mercaptobenzothiazole and dibenzothiazyl disulfide as 2 allergens responsible for tennis shoe dermatitis.

Although contact dermatitis from shoes is common, the causative allergen is frequently not known. Reliance cannot be placed on standard screening trays because such testing can be negative when testing to shoe materials is positive. Furthermore, the relevance of positive screening tests is almost never proven by extracting that allergen from the patient's shoes. We present a case of insole dermatitis to tennis shoes in which we directly isolated the causative allergens by step-by-step patch-test monitoring of active fractions. Chromatographic separation of the active fractions led to the isolation of 2 allergens, mercaptobenzothiazole (Captax) (MBT) and its dimer, dibenzothiazyl disulfide (Altax) (DBTD). Patch tests to DBTD were noticeably more potent than those to MBT. In what might be considered an obvious case of contact sensitivity to MBT, the actual allergen is DBTD. Using this method, unknown shoe allergens can be isolated, identified, and added to the shoe test tray of potential allergens.