Inflammatory mediators released from mast cells (MCs) through engagement of the high-affinity receptor for IgE (FcepsilonRI) have pivotal roles in chemical allergen-induced contact hypersensitivity (CHS) reactions, which suggests that the blockade of MC activation through FcepsilonRI stimulation may attenuate allergic contact dermatitis (CD). To address this possibility, we employed the following two approaches: (i) modulation of FcepsilonRI-mediated MC activation by introducing mutations in tyrosine residues of the FcepsilonRI beta-chain immunoreceptor tyrosine-based activation motif (ITAM) and (ii) blockade of FcepsilonRI-mediated MC activation employing a recombinant soluble ecto-domain of the human FcepsilonRIalpha-chain (rsFcepsilonRIalpha). In this study, we show that optimal MC activation through the FcepsilonRI beta-chain ITAM has essential roles in the onset of CHS to oxazolone (Oxa), a well-characterized chemical allergen. In addition, we demonstrate that administration of the rsFcepsilonRIalpha after sensitization successfully prevents murine CHS to Oxa. In a chronic CD model elicited by multiple challenges with low-dose Oxa, application of the rsFcepsilonRIalpha during the course of the challenges showed suppressive effects on CHS to Oxa. Taken together, our data indicate that inhibition of FcepsilonRI-dependent MC activation can suppress allergic CD.