Hello, The darkening of the skin at the neck area is called acanthosis nigricans. This happens due to certain conditions such as diabetes or other hormonal disease and also due to obesity. Certain medications may as well cause acanthosis nigricans. I would advise you to have a check with your doctor to rule out treatable diseases as treating the cause if the best way to address this condition. If no cause is identified, the doctor may prescribe local creams such as retinoids or creams with vitamin D. I hope this answers your query. I remain at your disposal for further medical assistance. Regards, Dr. Antoneta Zotaj General and Family Physician