Zinc (Zn) is essential for normal cell structure and physiology. Its deficiency causes growth retardation, neuronal degeneration, and immunodeficiency. Zn homeostasis is tightly controlled through Zn transporters and metallothioneins, which regulate Zn concentration and Zn distribution in individual cells, and contributes to Zn-binding protein in cells. Although many molecules involved in these processes have Zn-binding motifs, the molecular mechanisms underlying the role of Zn in the immune system have not been clarified. Recently, we and other groups have demonstrated that Zn plays diverse and specific roles in vivo and in vitro, in studies on the genetic knockout of Zn transporter functions. In this review, we discuss the impact of Zn on mast cell-mediated allergy and T cell-mediated immune responses. We also describe Zn dysregulation as a leading health problem in allergy and immune responses.