A disease called Acanthosis Nigricans. I also have this. See a dermatologist and they can give you some skin lightning creams to take the color away. I wish you the best of luck!
Hello,
Without examination, confirmation of a diagnosis is tough, but it can be due to hyperpigmentation of the skin. This darkening occurs when an excess of melanin, the brown pigment that produces normal skin color, forms deposits in the skin.
Treatment involves hydroquinone, azelaic acid, corticosteroids, tretinoin cream and laser treatment. Please discuss these options with your dermatologist before using them.
Hope it helps. Take care and please do keep me posted on how you are doing or if you have any additional queries. Warm regards.