Fifty years ago the first report of Immunoglobulin E (IgE) was published, and since then this antibody has revolutionized the diagnosis and management of allergic disease. Kimishige and Teruko Ishizaka, et al, initially described IgE after an extensive investigation of a substance that Coca and Cooke had called “reagin” as early as 1923.1 Little work occurred on “reagin” from the 1920’s until the 1960’s, when newer techniques had been developed that aided in the detection and identification of proteins. It was at this point that the Ishizakas described an anti-serum that was able to block the body’s allergic response, and called this molecule γE-globulin in their 1966 seminal paper.2 Interestingly, this molecule did not fix complement or induce a precipitin reaction like other immunoglobulins. Simultaneously, Hans Bennich and S.G.O. Johansson discovered a paraprotein in a leukemia patient that did not appear to be any of the known immunoglobulins at that time. They termed this paraprotein IgND and found that it had similar properties to reagin.3 Utilizing IgND antibodies and γE-globulin, both of which inhibited the Prausnitz-Kustner test (i.e., passive transfer of cutaneous anaphylaxis), Bennich, Johansson, and the Ishizakas, respectively, were able to demonstrate that the antibody isotype was in fact reagin.4 In 1968, the World Health Organization International Reference Center for Immunoglobulins officially named γE-globulin and IgND as Immunoglobulin E.5 The discovery of this new immunoglobulin opened the door to research and better understanding of the allergic response, as well as detection and diagnosis of specific allergic triggers. While these advancements in technology and understanding of allergic disease have developed over the last 50 years, there still remains a paucity of information on why IgE is produced and what its role is beyond allergic disease. Or, to paraphrase a popular rock song, “IgE, what is it good for?”