With the advances made in allergological diagnosis, thanks to the application of various in vitro immunological techniques, we have also learnt more about the immunological modifications produced during the course of the immunotherapy. Among the techniques which will detect immunological changes is the histamine release test, which will show a decrease in antigen-specific histamine release. On the other hand, both total IgE and IgG4 are modified in the course of this immunotherapeutic treatment.