4-Amino-2-nitrophenol is a brownish yellow compound used as an industrial dye intermediate and as a constituent of "semi-permanent" hair dyes under a trade name Rodol 42. 4-Amino-2-nitrophenol is formulated without an oxidizing agent. It is used in concentrations estimated at 0.1-1.0% in the "semi-permanent" hair dyes, which are applied as shampoos and remain on the hair for 20-40 minutes before they are rinsed out. Several toxicological studies suggested potential carcinogenicity and mutagenicity concerns for 4-Amino-2-nitrophenol.