Acanthosis nigricans is a skin condition characterized by dark, thick, velvety skin in body folds and creases. Most often, acanthosis nigricans affects your armpits, groin and neck.

With acanthosis nigricans, you may naturally be concerned about the appearance of your skin. Some steps may help lighten the affected areas of your skin. There's no specific treatment for acanthosis nigricans — but treating any underlying conditions, such as diabetes and obesity, may cause the changes in your skin changes to fade.