Toxicological Evaluation of Synthetic Hair Dye Products Available in Nigerian Markets: Focus on Aromatic Amine Content

Synthetic oxidative hair dyes contain aromatic amine precursors, many of which are suspected or confirmed human carcinogens, raising health concerns for frequent users and salon workers. This study evaluates the aromatic amine content of ten synthetic hair dye products widely available in markets across Abuja and Kaduna, North Central and North West Nigeria. Products were selected based on market prevalence survey across five cosmetic retail outlets. Aromatic amines including p-phenylenediamine, resorcinol, 4-aminophenol, and 2-amino-4-nitrophenol were extracted using a validated solvent extraction protocol and quantified by high-performance liquid chromatography with diode array detection. Results show that p-phenylenediamine was the most consistently detected compound, present in all ten products at concentrations ranging from 0.8 to 3.6 percent, with two products exceeding the EU Cosmetics Regulation maximum concentration of 2 percent. Resorcinol was detected in seven products. Total aromatic amine content was significantly higher in unbranded locally repackaged products than in imported brands. The study identifies regulatory shortcomings in the NAFDAC oversight of cosmetic products and recommends mandatory pre-market testing for prohibited and restricted aromatic amines, enhanced labelling requirements, and public awareness campaigns targeting frequent hair dye users about associated exposure risks. Keywords: hair dye, aromatic amines, p-phenylenediamine, HPLC, cosmetic safety