Summary: In recent years, there has been a steady increase in the prevalence of allergic diseases. Allergic immune response represents a complex network of cellular events involving numerous immune cells and mediators. It represents the interaction of innate and acquired immune response. The key role in the immune cascade is taken by histamine, a natural component of the body, which in the allergic inflammatory response is releasesd by the mast cells and basophils. The aim of this study was to highlight the role of histamine in allergic immunological events, their effect on Th1 and Th2 subpopulation of lymphocytes and the production of the corresponding cytokines, as well as the role of histamine blockers in the treatment of these conditions. Histamine achieves its effect by binding to the four types of its receptors, which are widely distributed in the body. Histamine blockers block a numerous effects of histamine by binding to these receptors. As a highly selective second-generation antihistamine, cetirizine not only achieves its effects by binding to H1 receptors, but also attenuates numerous events during the inflammatory process. Knowledge of the effects of histamine blockers, including cetirizine, may lead to the selection of proper therapy for the treatment of allegic diseases.