[Lichenoid contact dermatitis from the ink of a red pen].

Introduction: Numerous cutaneous inflammatory reactions have been reported in literature, after using red dyes; most of them are lichenoid reactions and occur after tattooing. Few reports have mentioned inflammatory complications after using red ink.

Case Report: A 21-year-old woman was examined for papular erythematous, pruritic lesions on the back of her left hand. They developed within the area of a red inked pen writing, a few days before. There was an isomorphic reaction on the cheek which was in contact with the hand during sleep. Diagnosis of lichen reaction to red ink was made, and histologically confirmed on the hand.

Discussion: We report the first case to our knowledge of lichen reaction to red inked pen, which can be compared to hypersensitivity reactions to red pigment reported in literature. A Koebner phenomenon by friction, usual with lichen, is possible, but doesn't explain the reaction on the cheek. A contact dermatitis to red pigment of ink can also be suggested, although mostly eczema-like reactions have so far been reported; it seems moreover that lichenoid reactions reported only occur after intradermal injection of pigment during tattooing. This contact mechanism would nevertheless explain both localizations of lichen reaction in our patient.