Acquired diffuse slate-grey facial dyspigmentation due to henna: an unrecognized cause of pigment contact dermatitis in Korean patients.

Henna is a vegetable hair dye that can be used by individuals who are sensitized to oxidative dyes due to low allergenicity. The reported incidence of slate-grey facial dyspigmentation following the use of henna hair dye is extremely rare. This study aimed to identify the clinical, dermoscopic, and histopathological features of slate-grey facial dyspigmentation following the use of henna hair dye in Korean patients. We identified all patients who presented with slate-grey facial dyspigmentation following usage of henna hair dye. Patients were further evaluated for clinical, dermoscopic, and histopathological findings along with their patch test results. All 11 patients were females with Fitzpatrick's skin phototype III or IV. Prominent slate-grey-coloured dyspigmentation on the lateral side of the face and neck was most common in eight (72%) patients. Under dermoscopic examination, a pseudo-network with grey dots was observed in all patients. Histopathological examination revealed liquefaction degeneration of the epidermal basal layer and pigmentary incontinence in the papillary dermis in all patients. The diagnosis of pigmented contact dermatitis following usage of henna was made based on the clinical, dermoscopic, and histopathological findings in all patients. Pigmented contact dermatitis associated with henna occurs mostly in middle-aged women and requires long-term treatment. Therefore, careful attention should be paid when henna is used to dye hair in this age group.