We investigated whether IgE receptors are expressed on sensory neurons in mice. Immunostaining revealed that the high affinity IgE receptor FcepsilonRI was expressed in cultured dorsal root ganglion cells and that FcepsilonRI-immunoreactive cells were mainly positive for the pan-neuronal marker protein gene product 9.5. Many FcepsilonRI-immunoreactive neurons were small or medium in size. IgE was bound to cultured neurons but not glial cells from the ganglia. FcepsilonRI-immunoreactive cells were also positive for the high affinity IgG receptor FcgammaRI. The expression level of FcepsilonRI was lower than that of FcgammaRI. FcepsilonRI-like immunoreactivity was localized on nerve fibers in the skin. The results suggest that IgE acts directly on primary sensory neurons as well as mast cells.