by EBSCO Medical Review Board


Acanthosis nigricans is a skin problem that results in brown or black velvet-like markings. They appear under the arms, in the groin, or on the back of the neck. It can affect any skin fold.


Causes may be:

  • High insulin levels
  • Hormonal problems
  • Faulty genes
  • Cancer

Risk Factors

This problem is more common in people who are Native American, Black, or Hispanic. Other things that may raise the risk are:

  • Being overweight
  • Having a family history of this problem
  • Resistance to insulin
  • Taking certain medicines that cause insulin to rise too high


Symptoms include velvety-looking, dark areas anywhere on the skin.


The doctor will ask about your symptoms and health history. A physical exam will be done. It will focus on the skin. This is often enough to make the diagnosis.

If the diagnosis is not certain, a skin biopsy may be done.

Endoscope in stomach
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The underlying cause will need to be treated. Some choices are:

  • Maintaining a healthy weight through diet and exercise
  • Stopping or changing medicines that may be causing insulin problems
  • Medicines to improve skin appearance, such as topical and oral retinoids
  • Laser therapy to improve skin appearance


To lower the risk of this problem:

  • Maintain a healthy weight through diet and exercise
  • Manage insulin levels


American Academy of Dermatology 

NORD—National Organization for Rare Diseases 


Canadian Dermatology Association 

Health Canada 


Acanthosis nigricans. EBSCO DynaMed website. Available at: Accessed October 29, 2020.

Phiske MM. An approach to acanthosis nigricans. Indian Dermatol Online J. 2014 Jul;5(3):239-249.

Revision Information

  • Reviewer: EBSCO Medical Review Board James P. Cornell, MD
  • Review Date: 09/2020
  • Update Date: 04/28/2021