Dihydroethidium, also known as hydroethidine, is a dye that can permeate viable cells and accumulate in the nucleus after it is dehydrogenated to ethidium bromide and is used to measure oxygen reduction in phagocytes during respiratory burst. In the presence of an oxidant it will fluoresce and has been used as a dye in flow cytometry. Studies have used Dihydroethidium to study alveolar macrophages, blood leukocytes, and epithelial cells, among others, and has be used to measure intracellular H2O2 and O2-, and reactive oxygen. Dyes and metabolites.