Evaluation of the immune status in vivo by the 2,4-dinitro-1-chlorobenzene contact allergy time (DNCB-CAT).

The time interval from starting continuous application of 2,4-dinitro-1-chlorobenzene (DNCB) epicutaneously until the appearance of an allergic contact reaction, i.e. 'contact allergy time' (CAT), was determined. In 34 patients initially 2.0% DNCB ointment was administered for 2 days, then 0.05% DNCB ointment was applied daily (group I). In 39 patients only the 0.05% DNCB preparation was used (group II). The median of DNCB-CAT was 11.2 +/- 0.8 days in group I and 22.3 +/- 3.7 days in group II (p less than 0.01). In patients older than 55 years DNCB-CAT was significantly longer than in younger patients. The medians of DNCB-CAT did not differ in male and female patients. In contrast to the conventional DNCB-sensitization procedures, the CAT method allows one to measure induction and elicitation phase quantitatively.