We examined whether different itch signals converge on the same dorsal horn neurons in mice. Intradermal injections of histamine and SLIGRL-NH2 (protease-activated receptor-2 agonist) induced scratching in naive mice and so did mosquito allergen in sensitized mice. These stimuli induced Fos expression in cells in the superficial dorsal horn. Fos-positive cells were mainly distributed within the isolectin B4-labeled region (inner aspect of lamina II) after histamine injection. In contrast, they were in the region dorsal to the isolectin B4-labeled region after injections of SLIGRL-NH2 and mosquito allergen. These results suggest that allergic itch signal is mediated by primary afferents expressing protease-activated receptor-2 and the neurons receiving signals of protease-associated itch and allergy-associated itch are different from those of histamine-induced itch.