IgE antibodies play a protective role against parasites and environmental toxins by its strong effector functions. However, aberrant IgE production can contribute to the development of allergic disorders, and thus is tightly regulated. Beside its very short half-life, IgE is normally produced only transiently and its affinity maturation is limited under physiological immune responses. Although such distinct characteristics of IgE among Ig classes are well-known, the underlying molecular mechanisms have not been understood until recently. Somatic or genetic defects of such mechanisms can lead to pathogenesis of allergic diseases. In this review, we summarize recent advances in our understanding of the mechanisms that control the production of IgE and formation of IgE-type humoral memory, focusing on the B cell immune responses.