DCFH-DA, 2',7'-Dichlorodihydrofluorescein diacetate (also called 2',7'-dichlorofluorescin diacetate), is hydrolyzed by cellular esterases to 2',7'-dichlorodihydrofluorescein (also called 2',7'-dichlorofluorescin) and is then oxidized to 2',7'-dichlorofluorescein primarily by H2O2.