Dihydroethidium (also called hydroethidium) is the chemically reduced form of the commonly used DNA dye ethidium bromide. The probe is useful to detect oxidative activities in viable cells, including respiratory burst in phagocytes. Dihydroethidium itself has blue fluorescence (Ex/Em: 355/420nm) in cells, while the oxidized form ethidium has red fluorescence (Ex/Em: 300/610 nm) upon DNA intercalation