“…The cause remains unknown. 1 Exogenous ochronosis (EO) is an uncommon disorder characterized by the deposition of microscopic, ochre-colored pigment in the dermis, giving rise to a blue-black hue in the skin. It is usually manifested by asymptomatic blue-black macules on photo exposed areas, predominantly on bony prominences (malar areas, temples, lower cheeks, and neck), and it is often associated with the prolonged application of various topical chemical substances, such as hydroquinone, phenol, resorcinol, mercurial, and picric acid, as well as with quinine injections and oral antimalarial agents.…”