Ablukast (Ro 23-3544) is tested for its efficacy in modulating dinitrofluorobenzene (DNFB)-induced allergic and croton oil-induced irritant contact dermatitis in mouse ears. Treatment shortly after elicitation of the dermatitis, and for up to 5 days thereafter, was moderately effective in suppressing DNFB-induced ear swelling in a dose-dependent fashion. Daily pre-treatment of the ears for 1 week causes a more marked reduction of DNFB-induced ear swelling during the first 48 h after elicitation.