Dose and timing studies for the optimization of contact sensitivity in the mouse.

We investigated the effectiveness of very low doses of the contact sensitizer dinitrofluorobenzene in sensitizing BALB/cJ mice. Surprisingly, the ear swelling reactions were greater with lower dinitrofluorobenzene doses, down to one-twentieth of doses commonly used. Although it is common practice to use much lower doses at challenge than at sensitization, we found greater reactions with lower doses at sensitization than at challenge. We also studied the timing of the development and waning of reactivity to dinitrofluorobenzene, dinitrochlorobenzene and oxazolone. Reactivity peaked at day 5 for dinitrofluorobenzene and dinitrochlorobenzene, and at day 3 for oxazolone. Reactivity waned by 3 weeks with dinitrofluorobenzene and oxazolone, and by day 7 with dinitrochlorobenzene. Pretreatment with cyclophosphamide caused a delay in the development and waning of reactivity.