The histology of blisters induced in rats using dry-ice or vacuum applied to the hind limb footpad has been examined by light microscopy and indirect fluorescence immunohistochemistry for substance P like immunoreactivity. The effects of sciatic nerve stimulation on plasma extravasation as determined by estimation of Evans Blue content of blister fluid has been examined. Plasma extravasation occurs in both blister types following nerve stimulation. Plasma extravasation may be induced by substance P released from nerve terminals in the blister wall. Vacuum induced blisters have less tissue and nerve damage and therefore less of an inflammatory response, but plasma extravasation is greater in thermal blisters. Blisters serve as a useful model for the study of neurogenic inflammation.