Chemical haptens induce a variety of allergic immune reactions by induction of hapten-specific T cells. Contact sensitizers such as the hapten trinitrochlorobenzene (TNCB) elicit an allergic response, which is confined to the area of antigen exposure. Despite this localized allergic response, we show here that the trinitrophenyl (TNP)-specific immune response is characterized by a rapid induction of CD8+ Tc1 type cytotoxic effector cells already after a single allergen contact which can be detected in all secondary lymphoid organs tested. We furthermore demonstrate that the rapid induction of CD8+ Tc1 effector cells correlates with an unusually high frequency of polyclonal TNP-specific CD8+ effector T cells with specificities for a variety of MHC class I binding TNP-peptides carrying the hapten in different positions. These data suggest that allergies to chemical haptens may in part be due to an unusually high frequency of polyclonal, allergen-specific effector cells which are detected in all secondary lymphoid organs.