Dark Velvety Skin on Your Neck or Armpits: What It Can Signal

If the skin on the back of your neck, in your armpits or in your groin has turned darker and thicker, with a texture like velvet, it has a name: acanthosis nigricans. The NHS¹ describes dry, dark patches that often come on gradually, sometimes itch, and sometimes carry tiny skin tags.¹ It’s usually harmless in itself, but the NHS says it can be a sign of an underlying condition and should be checked.¹

How common it is, and the diabetes link

• About 1 in 5 US adults. In a US study of 1,730 people, 19.5% of adults had it.² A 2024 review estimates 19.4%.³
• Twice the rate of type 2 diabetes. In that same study, 35.4% of adults with the patches had type 2 diabetes, compared with 17.6% of those without.²
• More common in some groups: estimated at 13.3% of African Americans, 5.5% of Latinos and 34.2% of Native Americans.² Some healthy people with no other condition get it, more often those with Black or brown skin.¹

What it can point to

Possible cause	What to mention at the visit
Higher body weight, the most common cause1	Recent weight change
Type 2 diabetes1	Thirst, peeing more, family history of diabetes
Hormone conditions: Cushing’s syndrome, PCOS (now also called PMOS), an underactive thyroid1	Irregular periods, new chin hair, tiredness, feeling cold
Medicines: steroids, or hormone treatments such as the pill12	When you started each one
Rarely, cancer, usually stomach cancer1	Patches that came on suddenly. That form tends to appear abruptly, in middle-aged people who aren’t overweight2

See what PCOS (PMOS) is, whether to remove skin tags, dark patches on the face and gum disease treatment and A1c.

What helps

• Treat the cause first. The NHS¹ says the patches should fade over time once the cause is treated, and that there’s no specific treatment for the patches themselves.¹
• For appearance, creams have the best evidence. A 2024 review of 19 trials gave its strongest recommendation to prescription tretinoin cream, with lesser support for adapalene gel, urea cream and a fractional CO2 laser.³
• It can weigh on you, and the same review notes it affects psychological well-being, especially for people with darker skin.³ It’s a fair thing to raise.
• Skip the scrubbing. These patches aren’t dirt. If you want to lighten them, see underarm lightening creams and the FDA first.

Try: “I’ve noticed dark, velvety skin on the back of my neck and in my armpits over the past year. Could we check my blood sugar and look for other causes?”

Skin, Head to Toe covers this in Chapter 9, “The Folds,” in a section called “The Velvety Clue.” Its Skin Sort puts velvety, thickened, darker skin in the folds in the Clue box: one check with a doctor, and a prompt one if a patch comes on fast or spreads quickly. See the book.