Tolerance of dinitrochlorobenzene, a contact sensitizer, in man

The contact sensitizer, dinitrochlorobenzene (DNCB), was applied according to several schedules of small weekly or biweekly doses to the buccal mucosa of 64 adult men. The responses of these men were then compared with those of 37 control subjects when all were simultaneously given a “sensitizing” series of applications of DNCB to the skin. Buccal administration of DNCB induced detectable contact sensitivity to DNCB in 39 of the 64 subjects. During the subsequent topical exposures, those buccally treated subjects who had been sensitized showed little rise in degree of sensitivity, while many of those who had not been sensitised failed to become sensitized. Control subjects showed a normal response to the same topical exposures, and quantitative tests at the end of the experiment showed that control subjects were significantly more sensitive to DNCB than were those previously exposed to the compound by the buccal route. Thus, application of DNCB to the buccal mucosa partially aborted later attempts to induce contact sensitivity to the same compound by topical application. There is some evidence that this tolerance was more effectively induced by lower doses of DNCB applied to the buccal mucosa at fortnightly intervals than by larger amounts given more frequently.