Skin changes are the only signs of acanthosis nigricans. You'll notice dark, thickened, velvety skin in body folds and creases — typically in your armpits, groin and back of the neck. The skin changes usually appear slowly. The affected skin may also have an odor or itch.
Consult your doctor if you notice changes in your skin — especially if the changes appear suddenly. You may have an underlying condition that needs treatment.