What is acanthosis nigricans? Acanthosis nigricans (AN) is a skin condition that causes darker, thicker skin that often feels like velvet. It usually forms in body folds and creases, such as the back of the neck, the armpits, and the groin. MedlinePlus, from the National Library of Medicine, says it can affect otherwise healthy people, but it is also linked to insulin resistance in diabetes and obesity. The American Academy of Dermatology (AAD) says it can be a sign of prediabetes and advises getting tested for diabetes.
Key takeaways
- AAD says acanthosis nigricans causes skin to darken and thicken, often with a velvety feel. It is not contagious and not harmful.
- AAD says it can be a sign of prediabetes or diabetes, and may be the first sign of either. AAD's advice is to get tested for diabetes.
- Other causes include some medicines, hormone conditions such as PCOS or thyroid disease, and family history.
- AAD says patches that appear suddenly can be a warning sign of cancer and need a dermatologist visit right away.
- MedlinePlus says acanthosis nigricans often disappears if the cause is found and treated.
What Does Acanthosis Nigricans Look Like?
AAD lists these signs. The skin with acanthosis nigricans may:
- Be brown or black in color
- Feel velvety and thicker than the skin around it
- Have skin tags
- Itch
- Have a bad odor
MedlinePlus says it usually appears slowly and does not cause any symptoms other than skin changes. AAD says it can take months or years to form.
AAD also says some people think a dye or something they touched has stained their skin, so they try scrubbing it away. Scrubbing will not get rid of acanthosis nigricans.
Where Does Acanthosis Nigricans Show Up?
The most common places, according to AAD, are:
- The back of the neck
- The armpits
- The groin, especially in skin folds and creases
AAD says patches can also form on the elbows, knees, knuckles, belly button, under the breasts, and on the face. Less often, they form on the lips, mouth, eyelids, palms, soles of the feet, or nipples. MedlinePlus says patches on the lips, palms, or soles are more common in people with cancer.
How Is Acanthosis Nigricans Linked to Diabetes?
MedlinePlus lists hormone imbalances that happen in diabetes and obesity, often called insulin resistance, as one cause. Insulin resistance means the body's cells do not respond well to insulin, so the body needs more insulin to move sugar out of the blood. DermNet, a dermatology reference, says the darkening and thickening of skin folds is thought to be due to insulin resistance.
AAD says acanthosis nigricans:
- Can be a sign of prediabetes, which raises your risk of getting diabetes
- Often forms on the back of the neck, where it may be the first sign that someone has diabetes or prediabetes
- Is more common in people who have diabetes
AAD notes that making lifestyle changes before diabetes develops can prevent diabetes. Learn more in our guides to what insulin resistance is, how to test for insulin resistance, and prediabetes symptoms.
Who Gets Acanthosis Nigricans?
AAD says anyone can get it, but some people have a greater risk. People most likely to get it are those who:
- Have overweight or obesity
- Are of Native American, African, Caribbean, or Hispanic descent
- Have family members with acanthosis nigricans
AAD says obesity is the most common cause. AAD also says completely healthy people get it too, and they tend to have family members with the same skin change. It can affect children and teens as well. AAD shows it on the hands of a 15-year-old. See our guide to signs of diabetes in kids.
What Else Can Cause Acanthosis Nigricans?
Diabetes is not the only cause. AAD and MedlinePlus list:
- Medicines. AAD names birth control pills, strong corticosteroids like prednisone, and niacin. MedlinePlus also names hormones such as human growth hormone.
- Hormone conditions. AAD names polycystic ovary syndrome (PCOS), thyroid disease, and problems with the adrenal glands.
- Genetic conditions. MedlinePlus names Down syndrome and Alström syndrome.
- Cancer. AAD says that when acanthosis nigricans develops quickly, it can be a sign of cancer, especially in the stomach, colon, or liver. MedlinePlus says the same for patches that spread fast over large areas.
If you take one of these medicines, do not stop it on your own. AAD says changing medicines might be an option, but that is a decision for your prescriber. See our guides to PCOS and diabetes and whether prednisone raises blood sugar.
Acanthosis Nigricans vs. Skin Tags vs. Dirt or Stains
| Question | Acanthosis nigricans | Skin tags | Dirt or a stain |
|---|---|---|---|
| What it looks like | Dark, thick, velvety patch | Small, soft growths, sometimes on a stalk | Surface color on the skin |
| Where it forms | Neck, armpits, groin, skin folds | Eyelids, neck, armpits, groin | Anywhere |
| Comes off with washing? | No; AAD says scrubbing will not remove it | No | Yes |
| Linked to diabetes? | Can be a sign of prediabetes or diabetes (AAD) | Many skin tags may be a sign of type 2 diabetes (AAD) | No |
Skin tags and acanthosis nigricans often show up together. Read more about whether skin tags are a sign of diabetes.
How Is Acanthosis Nigricans Diagnosed?
MedlinePlus and AAD say a doctor can usually diagnose it just by looking at your skin. A skin biopsy (a tiny skin sample) is needed only in rare cases, according to MedlinePlus.
Because it can point to another condition, AAD says you may need a blood test and other tests. MedlinePlus lists blood tests to check your blood sugar or other diabetes testing. If there is no clear cause, your doctor may order other tests, such as a scope exam of the digestive tract (endoscopy) or x-rays.
If you have not been tested for diabetes, ask about it. Our guide to when adults should be screened for type 2 diabetes explains the common tests.
How Is Acanthosis Nigricans Treated?
MedlinePlus says no treatment is needed, because acanthosis nigricans only changes skin color. The focus is on the cause. MedlinePlus says that when it is related to diabetes, insulin resistance, or obesity, addressing those conditions should be the focus of treatment.
AAD says many people see their skin clear when they get treatment for the cause. AAD adds that when people with obesity who have acanthosis nigricans lose a significant amount of weight, they often see their skin clear. AAD also notes that treating a cause like prediabetes may not completely clear the patches. Your care team can help you set goals that fit your health.
If you want clearer skin, AAD says a dermatologist may suggest:
- Prescription creams, ointments, or gels to lighten skin color
- Laser treatments to reduce skin thickness
- Antibiotics applied to the skin and antibacterial soaps to ease odor and discomfort
- Retinoids, as a cream or pill, to help clear the skin
AAD says none of these were designed just for acanthosis nigricans, and it can be hard to treat. Ask a dermatologist before trying any cream.
When Should You See a Doctor?
Right away: AAD says to make an appointment with a board-certified dermatologist right away if dark patches appear suddenly or spread quickly.
Prompt appointment: MedlinePlus says to contact your provider if you develop areas of thick, dark, velvety skin. Ask whether you should be tested for diabetes or prediabetes, and bring a list of every medicine and supplement you take.
Ongoing care: If you already have diabetes, tell your care team about the patches at your next visit.
Frequently Asked Questions
Does acanthosis nigricans mean I have diabetes?
Not always. AAD says acanthosis nigricans can be a sign of prediabetes or diabetes, and it may be the first sign of either. It can also be caused by some medicines, hormone conditions, family history, or rarely cancer. AAD advises getting tested for diabetes if you have it.
Can acanthosis nigricans go away?
It can. MedlinePlus says acanthosis nigricans often disappears if the cause can be found and treated. AAD says many people see their skin clear when the cause is treated, but treating a cause like prediabetes may not completely clear the patches. A dermatologist can treat the skin if needed.
Is acanthosis nigricans dangerous?
AAD says acanthosis nigricans is not contagious and not harmful on its own. It matters because it can be a warning sign of a health problem, such as prediabetes. AAD says patches that appear suddenly can be a warning sign of cancer and need a dermatologist visit right away.
Can you scrub off acanthosis nigricans?
No. AAD says vigorous scrubbing will not get rid of acanthosis nigricans. People sometimes think a dye or something they touched has stained their skin. Scrubbing can irritate the skin. A dermatologist can suggest treatments if you want the skin to look clearer.
Can kids get acanthosis nigricans?
Yes. AAD says anyone can get acanthosis nigricans, and it shows the condition on the hands of a 15-year-old. A doctor can check whether a child's patch is linked to prediabetes or another cause. Talk with your child's doctor about a new dark, velvety patch.
What medicines can cause acanthosis nigricans?
AAD lists birth control pills, strong corticosteroids like prednisone, and niacin. MedlinePlus also lists hormones such as human growth hormone. Do not stop any medicine on your own. Ask your prescriber whether a medicine could be the cause.
References
- MedlinePlus, National Library of Medicine. “Acanthosis nigricans.” Review date April 9, 2026. Accessed October 2026.
- American Academy of Dermatology. “Acanthosis nigricans: Overview.” Accessed October 2026.
- American Academy of Dermatology. “Acanthosis nigricans: Signs and symptoms.” Accessed October 2026.
- American Academy of Dermatology. “Acanthosis nigricans: Who gets and causes.” Accessed October 2026.
- American Academy of Dermatology. “Acanthosis nigricans: Diagnosis and treatment.” Accessed October 2026.
- American Academy of Dermatology. “Diabetes: 10 warning signs that can appear on your skin.” Accessed October 2026.
- Oakley A, Elghblawi E. “Skin problems associated with diabetes mellitus.” DermNet. August 2019. Accessed October 2026.
Next Steps
If you notice a dark, velvety patch, take a photo, note when you first saw it, and ask your doctor whether you should be tested for diabetes or prediabetes. Our hub guide explains how diabetes affects your skin more broadly.
For adults with type 2 diabetes or prediabetes who want lifestyle education alongside clinical care, the Done With Diabetes™ program organizes learning about meals, movement, sleep, and stress. It does not diagnose or treat skin conditions, insulin resistance, or diabetes, interpret test results, change medicines, or replace your care team.