Blood is significant biological evidence in forensic investigations, and before DNA analysis, it is frequently screened to verify its biological provenance. These presumptive tests use hydrogen peroxide (H 2O 2) as an oxidizing agent in conjunction with reagents such as Phenolphthalein (Php) and tetramethylbenzidine (TMB) to measure hemoglobin’s peroxidase activity. Although these compounds help detect the presence of blood, their genotoxic effects—mainly when H 2O 2 is present—have raised concerns about possible DNA destruction. This study uses the Comet test, a single-cell gel electrophoresis method that assesses DNA strand breakage without DNA extraction, to examine the genotoxic effects of TMB and Php on blood samples. Blood samples were subjected to different combinations of TMB, Php, and H 2O 2 to evaluate their impact on DNA integrity. The results showed that combining blood enhancement reagents and H 2O 2 caused oxidative DNA damage, forming 8-oxo-deoxyguanosine, a hallmark of DNA adducts. This study emphasizes that blood augmentation drugs should be carefully considered because they can degrade DNA, which could jeopardize forensic DNA analysis.