[Exogenous ochronosis, a little-known side effect of hydroquinone-containing ointments].

Two patients with exogenous ochronosis, an unfamiliar side effect of hydroquinone-containing bleaching creams, are presented. This disorder is characterized by progressive darkening of the area to which the cream is applied. Histologically there is deposition of yellow-brown pigment in the dermis, in addition to degeneration of collagen and elastic fibres. The chemical composition of the ochronotic material and the pathogenesis of this paradoxical effect of hydroquinone are unknown. Hydroquinone containing creams should not be used for longer than two years. If there is no improvement within six months, application should be discontinued.