Oxidative stress in cells can result in the appearance and accumulation of free aldehydes on DNA and proteins. Cayman's Aldehyde Site (DNA and Protein) Detection employs an aldehyde reactive probe (ARP), O-(biotinylcarbazoylmethyl) hydroxylamine, that reacts specifically with aldehyde groups resulting from protein or DNA modification. By using an excess amount of ARP, aldehyde sites in both protein and DNA can be converted to biotin-tagged aldehyde sites, which can be detected using avidin-conjugated reporters. Epigallocatechin Gallate (EGCG), a compound known to react with culture medium to generate H2O2 and cause DNA damage, is included to be used as a positive control. The kit is easy to use and can be easily adapted to high throughput screening for compounds imposing oxidative stress on cells or organisms.