Low-pulse energy Q-switched Nd:YAG laser treatment for hair-dye-induced Riehl's melanosis.

Riehl's melanosis, a form of dermatitis characterized by reticulate pigmentation, typically presents as a gray-brown to black hyperpigmentation on the face and neck. Among the various etiologic factors suggested, photoallergic reaction and pigmented contact dermatitis resulting from exposure to drugs, coal tar dyes, optical whitener, or other ingredients found in cosmetics are believed to be the major contributing factors in this disease. The histopathological features of Riehl's melanosis mainly consist of pigmentary incontinence along with infiltration of numerous dermal melanophages and lymphohistiocytes.1,2 Additionally, notable clinical improvements in the treatment of this condition have been reported for intense pulsed light (IPL) therapy, in comparison to long-term topical application of bleaching agents.2 Here, we report the cases of two Asian patients treated with a low-pulse energy 1,064-nm Q-switched (QS) Nd:YAG laser for hair dye-induced Riehl's melanosis on the face and neck. In conclusion, we observed that Riehl's melanosis on the face and neck was effectively and safely treated with a low-pulse energy 1,064-nm QS Nd:YAG laser. We suggest that this method can be used in Asian patients with Riehl's melanosis at risk of postinflammatory hyperpigmentation from excessive light or laser energy delivery.