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A to Z: Acanthosis Nigricans

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Acanthosis nigricans (ay-can-THO-sis NYG-ruh-cans) is a condition in which the skin thickens and darkens in places.

More to Know

In acanthosis nigricans, thick, dark, and sometimes streaky patches appear on the skin. The patches are harmless and aren’t contagious. They usually affect areas with skin folds, such as the neck, armpits, elbows, knees, and groin, but can appear anywhere on the body. Sometimes, it might seem that the skin is dark because it’s dirty, but this is not the case. Scrubbing the skin does not help and can cause irritation.


Acanthosis nigricans is more common in people who have high levels of the hormone insulin in their blood due to insulin resistance. Both conditions occur much more often in those who are overweight and at higher risk for developing type 2 diabetes. However, acanthosis nigricans also can be hereditary and occur in kids and teens who are otherwise healthy.

When acanthosis nigricans is suspected, the doctor may order tests to check for insulin resistance or diabetes.

Keep in Mind

The dark skin patches that appear in acanthosis nigricans are harmless, but people with this condition might have a higher risk for developing diabetes and other health problems.

In those who are overweight, reaching and maintaining a healthier weight through increased physical activity and dietary changes might help improve the skin’s appearance.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.