Dihydrofluorescein diacetate is a fluorescent probe for detecting intracellular oxidants. It is hydrolyzed by cellular esterases to dihydrofluorescein and is then oxidized to fluorescein primarily by H2O2. Dihydrofluorescein diacetate might be reactive toward a broad range of oxidizing reactions that may be increased during intracellular oxidant stress. Cell-loading studies indicate that dihydrofluorescein achieves higher intracellular concentrations than the other redox sensors such as Dihydrorhodamine 123 (Ex/Em: 490/514nm).