Here's exactly what you need to know about those velvety dark patches in body folds. . . . [ Acanthosis nigricans, elbows, knees, armpits darkness, how to get rid of dark skin, Glutathione as a skinlightening agent and in melasma: a systematic review Sarkar 2025 International Journal of Dermatology Wiley Online Library Acanthosis nigricans, also known as Dark neck black neck, is a skin condition that causes darker, thicker skin and that may feel velvety. It usually appears on the neck, folds of the Acanthosis nigricans is a medical sign characterised by brown to black, poorly defined, velvety hyperpigmentation of the skin. It can also be due to some underlying disease, so don't ignore & consult your doctor. . . #