Naphthol AS as a cause of pigmented contact dermatitis

Naphthol AS is a coupling agent of cotton dyeing. 2 elderly women with hyperpigmentation of the neck and limbs are described. Both felt itching on the neck, forearms, and lower extremities and noted hyperpigmentation a month later. Both had worn cotton flannel nightdresses in winter. Patch testing with cotton flannel and methanol extracts were positive, but after estraction with methanol, the residual flannel did not react. The methanol extracts of cotton flannel, were analysed. The patients were tested with 5 extracted components; Naphthol AS was found to be the causative agent.