Why won't this brown discoloration wash off my neck?
Acanthosis nigricans is a disorder that causes light-brown-to-black, velvety, rough areas or increased skin markings usually on the back and sides of the neck. The condition can also, at times, occur under the arms and in the groin. It won't wash off.

How did I get it?
Acanthosis nigricans may begin at any age. We do not know the exact cause of this condition. Rarely, the condition is associated with an endocrine disorder or a tumor. Acanthosis nigricans is sometimes associated with being overweight.

How is it treated?
Retin-A, 15% urea, Lac-Hydrin, alpha hydroxy acid, and salicylic acid are all prescriptions that may provide some improvement for this condition. There is no cure for acanthosis nigricans. Overweight individuals usually have dramatic improvement if they lose weight. When acanthosis nigricans develops, occasionally, a medical work-up will be done to determine whether or not the patient has a gland (endocrine) disorder or a tumor. In those who have a tumor or a gland disorder, correction of the underlying problem will often cure the acanthosis nigricans.