Paraphenylenediamine (PPD) is a synthetic compound that is widely used as a hair dye. This study investigated biochemical and histological effects after repeated PPD dermal application. 30 adult male albino rats (200± 20gms) were classified into two groups; group I, (control group) included negative and positive control subgroups, each consisted of 10 rats and group II (tested group). Tested group was subjected to repeated topical PPD application in a dose of 10mg/kg for 90 days. All groups were investigated for these laboratory biochemical parameters: Serum creatine phosphokinase CPK-MB, aspartate (AST) and alanine transferases (ALT), serum creatinine (S. Creat.), blood urea nitrogen (BUN) as well as serum potassium. All the mentioned parameters showed significant increase when compared to control group. ECG was done and revealed significant decrease of pulse rate and significant prolongation of PR, QRS and QT intervals in tested group. In-addition, to biochemical and ECG investigations; histological examination was done for; cardiac, hepatic, renal and testicular tissues. Cardiac, hepatic, renal, and testicular tissues of tested group showed evident changes.  These changes were more obvious in Cardiac, renal, and testicular tissues when compared to control.