The current study was carried out to elucidate the immunoregulatory changes induced by venom immunotherapy (VIT) in bee or wasp allergic subjects. All subjects included in this study had a history of severe systemic allergic reactions to stings of the respective insect as well as positive skin tests with the respective venom or venom‐specific IgE in the sera. Parameters assessed in peripheral blood mononuclear cells (PBMC) before and after initiation of VIT (rush therapy reaching a maintenance dose of 100 μg venom injected subcutaneously within 1 week) were expression of CD3, CD4, CD8, CD45RA, CD45R0, interleukin (IL)‐2 receptor (R)α, IL‐4R, IL‐12R, FcσRII, CD40, and CD40 ligand (CD40L), cells producing interferon (IFN)‐γ and IL‐10 after stimulation with phorbol 12‐myristate 13‐acetate + ionomycin in the presence of monensin measured by flow cytometry; secretion of IFN‐γ, IL‐4, and IL‐10 measured by ELISA (IFN‐γ and IL‐10 were additionally measured by PCR), and proliferation after stimulation with the respective venom. Significant decreases were observed after VIT for proliferative response to venom and venom + IL‐4, IL‐4 secretion, FcσRII, CD40, and CD40L expression. Significant increases were observed after VIT for IFN‐γ concerning the amount secreted and the number of producing cells, and IL‐10. IL‐10 was mainly produced by CD4⁺ cells that were negative for IFN‐γ, but some double‐positive (IL‐10 and IFN‐γ) cells were always detected. Addition of blocking anti‐IL‐10 antibodies, but not isotype control antibodies, prevented down‐regulation of proliferation (but not IL‐4 secretion) and further enhanced IFN‐γ secretion after VIT. These data indicate that in insect venom allergic subjects, VIT not only induces a rapid shift in cytokine expression from Th2 to Th1 cytokines, but also leads to induction of the immunosuppressive cytokine IL‐10, which may be important for the limitation of potentially harmful allergen‐specific Th1 responses. The described changes in cytokine expression may be responsible for subsequent increases in allergen‐specific IgG and decreases in IgE production, as well as suppressive activity observed in earlier studies.