Under normal conditions, immune responses in the lung are suppressed, resulting in low antigen-specific serum antibody titers after intratracheal immunization of rodents. We attempted to determine whether mild inescapable electric foot-shock stress, immediately followed by intratracheal instillation of trinitrophenyl-conjugated keyhole limpet hemocyanin, could enhance the primary and secondary humoral immune responses in male Wistar rats. This acute emotional stress paradigm and subsequent intratracheal administration of trinitrophenyl-conjugated keyhole limpet hemocyanin resulted in a dramatic increment of trinitrophenyl-specific immunoglobulin isotype concentrations in serum, including IgE. Analysis of paratracheal lymph node and spleen tissue for trinitrophenyl-specific antibody-forming cells revealed that the increased specific antibody concentrations resulted from a local production in the paratracheal lymph nodes. Because the presence of aeroantigen-specific IgE is associated with diseases such as allergic asthma, we advocate the view that acute emotional stress can contribute to the onset or severity of allergic asthma by lowering the threshold of induction of aeroantigen-specific IgE production in the lungs.