Immunotherapy with wasp allergen leads to a variety of specific immunological changes. It is unknown, however, whether unspecific effects also occur, and which parameter shifts might indicate treatment success. Therefore, data of patients who had completed immunotherapy with wasp venom were analysed retrospectively for a change in the following parameters after therapy: threshold of skin tests with wasp venom, total and specific serum IgE, specific serum IgG and IgG4, and binding of IgE and IgG4 to major wasp venom allergens. Reactions to field stings were explored. A significant increase in the skin test threshold and a significant decrease in total serum IgE, specific serum IgE and major wasp allergens binding IgE were found. Concentrations of specific serum IgG and IgG4 increased. Patients with corresponding changes in at least three specific parameters did not report severe reactions to verified field stings after therapy. The marked decrease in total serum IgE indicates that wasp immunotherapy has wide-ranging immunological effects, and it appears reasonable to check combinations of several parameters for treatment control.