Have you ever noticed dark, velvety patches of skin around your neck, under your arms, or in other body folds and wondered what they mean?
For many people, these skin changes appear gradually and don’t cause pain or itching. Because they often develop slowly, they’re easy to ignore or mistake for dirt, poor hygiene, or simple skin discoloration. But in some cases, these patches can be a sign that your body is trying to tell you something important.

One possible cause is acanthosis nigricans, a skin condition that is often linked with insulin resistance, obesity, hormonal disorders, certain medications, or, more rarely, other underlying medical conditions.
The good news is that acanthosis nigricans itself is not contagious, and it is not caused by poor hygiene. While it isn’t dangerous on its own, it can sometimes be a clue that it’s worth discussing your
overall health with a healthcare professional.
Let’s take a closer look at what it is, why it happens, and when it’s a good idea to seek medical advice.
I/hot Is Acanthosis Nigricans?

Let’s take a closer look at what it is, why it happens, and when it’s a good idea to seek medical advice.
What Is Acanthosis Nigricans?
Acanthosis nigricans is a skin condition that causes areas of skin to become:
Darker than the surrounding skin
Thicker
Velvety in texture
The discoloration may range from light brown to dark brown or gray, depending on a person’s natural skin tone.
The affected skin often feels soft or
slightly raised rather than rough or scaly.
Where Does It Usually Appear?

The condition most commonly develops in skin folds, including:
The back or sides of the neck
Under the arms (armpits)
The groin
Elbows
Knees
Knuckles
Under the breasts
Less commonly, it can appear on:
The face
Belly button
Hands
Lips
What Causes Acanthosis Nigricans?
Acanthosis nigricans isn’t a disease by

Acanthosis nigricans isn’t a disease by itself. Instead, it’s often a sign associated with another condition or factor.
1. Insulin Resistance
The most common cause is insulin
resistance, a condition in which the body’s cells don’t respond well to insulin.
To compensate, the body produces more insulin, and high in levels may stimulate skin cells to grow more rapidly, leading to thickened, darker patches.
Insulin resistance is commonly associated with:
Prediabetes
Type 2 diabetes
Metabolic syndrome

Metabolic syndrome
Not everyone with insulin resistance develops acanthosis nigricans, but the two are frequently linked.
2. Excess Body Weight
People who are overweight or obese are more likely to develop insulin resistance, making acanthosis nigricans more common in this group.
In some individuals, gradual weight loss and improved metabolic health may lead to improvement in the skin changes.
3. Hormonal Conditions
Several hormone-related conditions may increase the likelihood of developing acanthosis nigricans, including:
Polycystic ovary syndrome (PCOS)

4. Certain Medications
Some medications have been associated
with acanthosis nigricans, including:
High-dose corticosteroids
Some hormonal medications
High-dose niacin
Certain treatments that affect growth hormones
If you notice new skin changes after starting a medication, don’t stop taking it on your own. Speak with your healthcare provider.
5. Genetics
In some families, acanthosis nigricans can occur due to inherited genetic factors.

This form is much less common and may appear during childhood without being linked to obesity or diabetes.
6. Rare Medical Conditions
Rarely, acanthosis nigricans can be associated with certain internal cancers,
particularly stomach (gastric) cancer.
This form usually develops suddenly, spreads quickly, and may involve unusual locations such as the mouth or palms.
Although this possibility sounds alarming, it’s important to remember that most cases are not related to cancer.
Common Symptoms
Besides darker skin, people may notice:
Thickened skin

The skin changes themselves are usually harmless.
However, because acanthosis nigricans may be associated with conditions such as insulin resistance or hormonal disorders, it’s worth discussing with a healthcare professional, especially if the patches are new or changing.
Treating the underlying cause often helps improve the appearance of the skin over time.
How Is It Diagnosed?
A healthcare provider can often recognize acanthosis nigricans by examining the skin.
Depending on your situation, they may
recommend tests such as: