Darkening of the neck is usually considered obesity acanthosis nigricans, also known as benign acquired acanthosis nigricans, and in the past also called pseudoacanthosis nigricans. This disease can occur in both men and women and is most common in adults, but can sometimes involve children. Dark-skinned individuals who are also obese are more likely to develop the disease. The rash is usually small pigmented patches with velvety thickening of the skin, often accompanied by multiple dermatomes, which do not simply show a black neck, but even in the armpits, groin, buttocks, etc., also appear black, but there is no special drug to treat this disease, and generally do not need special treatment, with weight loss, the rash can gradually fade, but there is also a deepening of color, is persistent The situation exists. However, if not only the neck is black, but also the skin of other parts of the body also appear short-term rapid darkening, as well as other conditions, need to pay attention to, should promptly go to the hospital to exclude the possibility of other diseases such as malignant acanthosis nigricans.