The efficacy of allergen immunotherapy for the treatment of allergic rhinoconjunctivitis with or without seasonal bronchial asthma and anaphylaxis caused by the sting of the hymenoptera class of insects has been clearly demonstrated in numerous well-designed, placebo-controlled trials. Immunotherapy whether by subcutaneous injection of allergen extract or by oral/sublingual routes modifies peripheral and mucosal TH2 responses in favour of TH1 responses and augments IL-10 synthesis by TRegs both locally and by peripheral T cells. Recent researches into the cellular and molecular basis of allergic reactions have advanced our understanding of the mechanisms involved in allergic diseases. They have also helped the development of innovative approaches that are likely to further improve the control of allergic responses in the future. Novel approaches to immunotherapy that are currently being explored include the use of peptide-based allergen preparations, which do not bind IgE and therefore do not activate mast cells, but reduce both Th1 and Th2-cytokine synthesis, while increasing levels of IL-10. Alternative strategies include the use of adjuvants, such as nucleotide immunostimulatory sequences derived from bacteria CpG or monophosphoryl lipid A that potentiate Th1 responses. Blocking the effects of IgE using anti-IgE such as omalizumab, a recombinant humanized monoclonal antibody that selectively binds to IgE, has been shown to be a useful strategy in the treatment of allergic asthma and rhinitis. The combination of anti-IgE-monoclonal antibody omalizumab with allergen immunotherapy has proved beneficial for the treatment of allergic diseases, offering improved efficacy, limited adverse effects, and potential immune-modifying effects. This combination may also accelerate the rapidity by which immunotherapy induces TReg cells. If allergic diseases are due to a lack of allergen-specific TReg cells, then effective therapies should target the induction and the development of TReg cells producing cytokines such as IL-10.