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Background The involvement of a shift from T H 2 to T H 1 responses in peripheral blood in pollen subcutaneous immunotherapy (SCIT) has been contentious, partly because of difficulties analyzing antigen-specific T H cells. Objectives To use recent technical advances to establish a more direct and simple method to analyze antigen-specific T H cells and to clarify the involvement of a T H 2/T H 1 shift in peripheral blood in pollen specific immunotherapy. Methods After short-term (6-hour) antigen stimulation, antigen-specific T H cells in peripheral blood of Japanese children and young adults with Japanese cedar pollinosis undergoing SCIT were analyzed by multicolor flow cytometry for the presence of the activation marker CD154 and intracellular cytokines. Results Twenty-eight patients between 5 and 22 years of age were enrolled in the study; 22 had started SCIT after enrolling in the study (SCIT group), and the remaining 6 were planning to start SCIT in the next off-season (control group). The number of Japanese cedar–specific interleukin (IL) 5–, IL-4–, interferon γ–, IL-17A–, IL-10–, and tumor necrosis factor α–producing T H cells without antigen-driven cell proliferation was determined. The seasonal increase in the number of Japanese cedar–specific IL-5– and IL-4–producing T H cells seen in the control group was suppressed in the SCIT group ( P Conclusion We report a powerful method for the analysis of antigen-specific T H cells in peripheral blood. This method will contribute to our understanding of immune mechanisms of immunotherapy and help us develop more sophisticated allergen specific immunotherapy.