Black dermographism, meaning “black writing on the skin,” is the phenomenon in which stroking certain metals on the skin creates a black line. This phenomenon was first reported in 1879, and several causes have since been postulated within the medical and metal industries.1
A 40-year-old woman reported an asymptomatic black smudge that would occasionally develop on her finger under her wedding ring and on her face when rubbing it with this ring. She wore her ring every day, but the line on her finger appeared only sporadically; she recalled that the discoloration possibly coincided with her menstrual cycle. This reaction dated back as long as she could remember, was reproducible with jewelry of 10- to 24-karat gold, and occurred no matter the brand of cosmetics or medication she applied. She was able to create the black line when her skin was devoid of topical agents, such as immediately after stepping out of the shower. The black smudge lasted 10 to 15 minutes before disappearing without manipulation. She demonstrated this short-lived black dermographism, which lasted 10 minutes before quickly fading (Figure).
Lowe E, Lim S. Black Dermographism. JAMA Dermatol. 2017;153(3):352–353. doi:10.1001/jamadermatol.2016.4554
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