Do you have diabetes or insulin issues? It could be a sign of that
Acanthosis nigricans is a disorder that may begin at any age. It causes velvety, light-brown-to-black, markings usually on the neck, under the arms or in the groin. Acanthosis nigricans is most often associated with obesity.
Eating too much of the wrong foods, especially starches and sugars, can cause insulin resistance. This will result in elevated insulin levels. Most patients with acanthosis nigricans have a higher insulin level than those of the same weight without acanthosis nigricans. Elevated levels of insulin in most cases probably cause acanthosis nigricans. The elevated insulin levels in the body activates insulin receptors in the skin, forcing it to grow abnormally. Reducing the circulating insulin by dieting or medication can lead to improvement of the skin problem.