The kit is a solid sandwich enzyme-linked immunosorbent assay for the detection of human IL-4. An anti-human IL-4 monoclonal antibody has been absorbed onto the wells of the microtiter strips provided. Samples including specimens or standards were pipetted into wells. The human IL-4 in specimens or standards would be captured by the coated antibody and the free others were removed by washing. The human IL-4 biotin-conjugated antibody was added and binds to human IL-4 captured by the first antibody, which formed a sandwich. Streptavidin-HRP would be added and binds to the biotin-conjugated antibody, then free Streptavidin-HRP would be removed during a wash step. After this, a substrate solution would be added and catalyzed by the HRP, and a colored product is formed. The intensity of the colored product is used to calculate in proportion to the amount of human IL-4 in the original specimen.