My electrologist had to use this on the back of my neck, since the hairs there are blonde and very small. It wiped right off with no problem, but a friend warned me she’d heard horror stories about it getting “Stuck” in the skin and leaving permanent black marks. I think she’s thinking of the carbon dye they used to use with the old-timey “laser hair removal” but I’m not sure. I don’t want to use it again until I know it’s not going to make me up. Someone mentioned brown eyeshadow for this purpose. I do need something, because otherwise the hairs are impossible to see.