Riehl's melanosis.

In Riehl's melanosis, first observed in 1917, facial hyperpigmentation, most pronounced on the forehead and in the zygomatic and/or temporal regions is the dominant symptom. Riehl could find no explanation for the condition, but suggested that certain foods used during the war could be responsible. Riehl's melanosis has later been observed in dark-complexioned people in whom hyperpigmentation with pigment incontinence may be the main sign of contact dermatitis caused by certain allergens. Riehl's melanosis is today almost synonymous with pigmented contact dermatitis of the face. The commonest cause has been sensitizing chemicals in cosmetics.