Immunoglobulins (Igs) are a critical component of the adaptive immune system of both man and mouse. The ability to detect and characterize Igs is an invaluable technique for immunology in either a research or a clinical setting. The advent of enzyme-linked immunosorbent assays (ELISAs) and monoclonal antibody technology has proven instrumental for advancing the science of Ig biology. IgE is of interest as it is the primary Ig responsible for allergic reactions ranging from allergic rhinitis to anaphylaxis. Here, we describe the history behind the IgE discovery and the protocol for purifying IgE and anti-IgE in the mouse. This is followed by our ELISA protocol for mouse IgE detection.