Have you ever seen dark, soft-looking patches of skin on your neck, under your arms, or in other skin folds and wondered why they appeared?
For many people, these patches develop slowly and do not hurt or itch. Because they appear little by little, they are often mistaken for dirt, poor washing, or normal skin discoloration. However, in some cases, they may be a sign that your body is trying to tell you something.
One possible cause is acanthosis nigricans, a skin condition that is commonly linked to insulin resistance, excess weight, hormone problems, certain medicines, or, in rare cases, other health conditions.
The good news is that acanthosis nigricans is not contagious and is not caused by poor hygiene. While the condition itself is usually not harmful, it can be a sign that you should talk to a healthcare professional about your overall health.
Let’s learn more about what acanthosis nigricans is, why it happens, and when you should seek medical advice.
What Is Acanthosis Nigricans?
Acanthosis nigricans is a skin condition that causes certain areas of the skin to become:
- Darker than the surrounding skin
- Thicker than normal
- Soft and velvety to the touch
The color of the affected skin may range from light brown to dark brown or gray, depending on a person’s natural skin tone.
The Affected Skin
The affected skin usually feels soft, thick, and velvety instead of rough or flaky.
Where Does It Usually Appear?
Acanthosis nigricans most often appears in areas where the skin folds, such as:
- The back or sides of the neck
- Under the arms (armpits)
- The groin
- Elbows
- Knees
- Knuckles
- Under the breasts
In some cases, it may also appear on the:
- Face
- Belly button
- Hands
- Lips
What Causes Acanthosis Nigricans?
Acanthosis nigricans is not a disease by itself. It is often a sign of another health condition or factor.
1. Insulin Resistance
The most common cause is insulin resistance, which happens when the body’s cells do not respond well to insulin.
To make up for this, the body produces more insulin. High insulin levels can cause skin cells to grow faster, leading to dark, thick patches of skin.
Insulin resistance is often linked to:
- Prediabetes
- Type 2 diabetes
- Metabolic syndrome
Not everyone with insulin resistance develops acanthosis nigricans, but the two are often connected.
2. Being Overweight
People who are overweight or obese are more likely to develop insulin resistance, which increases the chance of getting acanthosis nigricans.
For some people, losing weight and improving their overall health may help the skin look better over time.
3. Hormone Problems
Certain hormone-related conditions may also increase the risk, including:
- Polycystic ovary syndrome (PCOS)
- Cushing syndrome
- Hypothyroidism
- Other hormone disorders
4. Certain Medicines
Some medicines have been linked to acanthosis nigricans, such as:
- High-dose corticosteroids
- Some hormone medicines
- High-dose niacin
- Medicines that affect growth hormones
If you notice dark skin patches after starting a new medicine, do not stop taking it on your own. Talk to your healthcare provider first.
5. Family History
In rare cases, acanthosis nigricans runs in families because of inherited genes. This type may appear during childhood and is not always linked to obesity or diabetes.
6. Rare Health Conditions
In uncommon cases, acanthosis nigricans may be linked to certain internal cancers, especially stomach cancer.
This type usually appears suddenly, spreads quickly, and may affect unusual areas such as the mouth or the palms of the hands.
Although this can sound worrying, remember that most cases are not related to cancer.
Common Symptoms
Besides dark patches, people may notice:
- Thicker skin
- A soft, velvety feel
- Mild itching (sometimes)
- A slight odor in skin folds
- Patches that slowly spread over time
Most people do not feel any pain.
Is It Dangerous?
The skin patches themselves are usually harmless.
However, because they can be linked to conditions like insulin resistance or hormone problems, it is a good idea to see a healthcare professional, especially if the patches are new, spreading, or changing.
Treating the underlying cause often helps improve the skin over time.
How Is It Diagnosed?
A healthcare provider can often identify acanthosis nigricans by examining your skin.
They may also recommend tests such as:
- Blood sugar (glucose)
- Hemoglobin A1C
- Fasting insulin
- Cholesterol levels
- Hormone tests
If the patches appear suddenly or look unusual, more tests may be needed.
Can It Be Treated?
Treatment focuses on finding and treating the underlying cause. As the health condition improves, the appearance of the skin may also improve over time.
Treatment Depends on the Cause
If It’s Caused by Insulin Resistance
Improving blood sugar levels through healthy habits or medicine (if recommended by a doctor) may help the dark patches fade over time.
If It’s Related to Being Overweight
For some people, losing weight gradually can reduce insulin resistance and improve the appearance of the skin.
If It’s Caused by a Medicine
Your healthcare provider may decide if changing your medication is the best option.
Do not stop taking any prescribed medicine without talking to your doctor first.
Skin Care Tips
Creams alone usually won’t treat the condition, but these simple tips may help keep your skin healthy:
- Wash your skin gently with a mild cleanser.
- Use moisturizer regularly.
- Avoid scrubbing the skin too hard.
- Wear loose clothing if rubbing causes irritation.
- Protect exposed skin from too much sunlight.
Remember, these dark patches are not caused by dirt, so scrubbing harder will not remove them and may make the skin more irritated.
When Should You See a Doctor?
Talk to a healthcare provider if:
- The dark patches appear suddenly.
- They spread quickly.
- They become painful, itchy, or irritated.
- You have increased thirst, frequent urination, or unexplained weight changes.
- The patches appear in unusual places, such as the mouth or the palms of your hands.
- You are worried about diabetes or another health condition.
Getting checked early can help find and treat the underlying cause.
Can It Be Prevented?
Not every case can be prevented, but keeping your body healthy may lower the risk.
Healthy habits include:
- Eating a balanced diet
- Exercising regularly
- Maintaining a healthy weight
- Managing your blood sugar if you have diabetes or prediabetes
- Having regular medical checkups
Frequently Asked Questions
Is acanthosis nigricans contagious?
No. It cannot spread from one person to another.
Is it caused by poor hygiene?
No. It is not caused by poor hygiene, and washing or scrubbing harder will not make it disappear.
Will the dark patches go away?
They may improve after the underlying cause is treated. However, this can take several months, and results vary from person to person.
Can children get acanthosis nigricans?
Yes. Children can develop this condition, especially if they are overweight or have insulin resistance. A medical checkup is important to find the cause.
Does everyone with acanthosis nigricans have diabetes?
No. Although it is often linked to insulin resistance, it can also be caused by other health conditions, certain medicines, or inherited factors. Some people with acanthosis nigricans do not have diabetes.
Final Thoughts
Dark, velvety skin patches may seem harmless, but they should not be ignored. Acanthosis nigricans is often a sign that your body may be dealing with insulin resistance or another underlying health condition. While the skin changes themselves are usually not dangerous, they can help detect health problems early.
If you notice new or changing dark patches, especially on your neck, underarms, or other skin folds, consider seeing a healthcare provider. They can help identify the cause and recommend the right treatment. With proper care and healthy lifestyle changes, many people notice improvements in both their skin and overall health over time.