One Step HRP Detection System is a kit that consists of four reagents, and is used for the visualization procedure of immunohistochemical staining of samples fixed with formalin or glyoxal and embedded in paraffin blocks. Peroxide Block is used to block endogenous peroxidases, a procedure necessary to eliminate background staining and false positive results. The technology of the polymerized secondary antibody conjugated with peroxidase enables blocking of endogenous biotin and its background signal. DAB Concentrate / DAB Substrate consists of two components – DAB chromogen concentrate and DAB substrate. With the presence of the peroxidase enzyme conjugated to the secondary antibody, DAB forms a brown precipitate not soluble in alcohol and xylene at the location of the antigen. The One Step HRP Detection System is effective with mouse and rabbit primary antibodies.