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 neck. The skin changes appear slowly, sometimes over months or years. The affected skin may also smell bad or itch.
When to see a doctor
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.