Acanthosis nigricans is a skin condition that causes dark, thick, velvety patches to form on certain areas of the body. It most commonly appears on the neck, armpits, and groin. While it is not contagious or dangerous on its own, it can be a sign of an underlying health condition. Understanding what causes it — and when to get help — is important for your overall health.
What Is Acanthosis Nigricans?
Acanthosis nigricans is not a disease by itself. Instead, it is usually a visible sign that something else is happening inside your body. The skin changes can appear gradually over months or even years.
The affected skin looks darker than the surrounding area. It often feels thick and rough, similar to velvet. Some people also notice a mild odour coming from the affected folds of skin, especially in the armpits or groin.
This condition affects people of all ages, including children. However, it is more common in adults who have certain medical conditions, particularly those related to blood sugar and insulin levels. Learn more about acanthosis nigricans on Mayo Clinic.
Common Causes of Acanthosis Nigricans
There are several reasons why acanthosis nigricans develops. The most common cause is insulin resistance. This means the body’s cells do not respond properly to insulin, the hormone that controls blood sugar. As a result, the pancreas produces more insulin, and high levels of insulin in the blood can trigger skin cells to grow too quickly.
Furthermore, certain conditions and factors are strongly linked to this skin change.
Insulin Resistance and Type 2 Diabetes
Insulin resistance is the leading cause of acanthosis nigricans. Many people with this skin condition will eventually receive a diagnosis of prediabetes or type 2 diabetes. In Canada, over 11 million people live with diabetes or prediabetes, making this a very relevant concern.
If you notice dark skin patches and you also feel unusually thirsty, tired, or need to urinate frequently, speak with your family doctor as soon as possible. These symptoms together can point to blood sugar problems.
Obesity
Carrying excess body weight is another major risk factor. The more excess weight a person carries, the higher their risk of developing insulin resistance — and therefore acanthosis nigricans. However, this condition can also affect people at a healthy weight, so body size alone does not tell the full story.
Hormonal Disorders
Conditions that affect hormones can also trigger acanthosis nigricans. These include polycystic ovary syndrome (PCOS), thyroid disorders, and Addison’s disease. All of these conditions change the way the body handles hormones, which can, in turn, affect skin cell growth.
Medications
Certain medications can cause or worsen acanthosis nigricans. These include high-dose niacin (a B vitamin), birth control pills, corticosteroids, and some drugs used to treat HIV. If you recently started a new medication and noticed skin changes, mention this to your doctor or pharmacist.
Genetics
In some cases, acanthosis nigricans runs in families. If a close family member has this skin condition, you may be more likely to develop it too. This inherited form is usually benign, meaning it is not linked to a serious underlying illness.
Who Is Most at Risk?
Acanthosis nigricans can affect anyone, but certain groups are more likely to develop it. Understanding your personal risk factors can help you take action early.
People who are most at risk include:
Those with insulin resistance or type 2 diabetes
People with obesity or metabolic syndrome
Individuals with PCOS or other hormonal conditions
People with a family history of the condition
Those taking medications linked to skin changes
Certain ethnic groups, including Indigenous, Hispanic, and South Asian populations, who have higher rates of insulin resistance
In Canada, health disparities mean that some communities face higher risks of conditions like diabetes and insulin resistance. Provincial health programmes and community health centres are important resources for early screening and support.
Symptoms and Where It Appears
The main symptom of acanthosis nigricans is a change in skin colour and texture. The affected skin becomes darker — often brown or black — and feels thick or velvety to the touch. It may also itch or have a slight odour.
Most Common Body Locations
Acanthosis nigricans most often appears in skin folds and creases. These are areas where skin rubs together or where warmth and moisture build up.
Common locations include:
Neck: Often the back or sides of the neck
Armpits: One of the most frequently affected areas
Groin and inner thighs: Especially in people with obesity
Elbows and knees: Less common but possible
Knuckles and finger joints: Seen in some cases
Belly button area: Particularly in people with larger abdominal girth
In rare cases, the condition can appear on the lips, palms, or soles of the feet. This unusual pattern may sometimes be linked to a more serious underlying condition, such as certain cancers. Therefore, it is important to report any sudden or widespread skin changes to your doctor right away.
How Is Acanthosis Nigricans Diagnosed?
A doctor can usually diagnose acanthosis nigricans by looking at the skin. No special test is needed to identify the skin changes themselves. However, finding the underlying cause requires further investigation.
Your family doctor will likely ask about your medical history, current medications, and any family history of diabetes or hormonal conditions. They may also order blood tests to check your blood sugar levels, insulin levels, and thyroid function. In some cases, they may refer you to an endocrinologist — a specialist in hormone-related conditions — or a dermatologist for further evaluation.
In Canada, your provincial health plan covers most of these diagnostic tests when ordered by a physician. Ask your family doctor what is covered under your provincial plan. Visit Health Canada for information on health coverage in your province.
Treatment Options for Acanthosis Nigricans
There is no single treatment that directly removes the dark patches of acanthosis nigricans. The most effective approach is to treat the underlying cause. When the root problem is addressed, the skin often improves on its own over time.
Treating the Underlying Condition
If insulin resistance or type 2 diabetes is the cause, managing blood sugar is the first priority. This may involve lifestyle changes like eating a balanced diet rich in fibre, increasing physical activity, and, in some cases, taking medication such as metformin.
For people with obesity, even modest weight loss can lead to noticeable improvements in the skin. Losing five to ten percent of body weight can make a real difference in both insulin sensitivity and skin appearance.
If a medication is causing the skin changes, your doctor may adjust the dose or switch you to a different drug. Never stop taking a prescribed medication on your own — always speak with your doctor first.
Skin-Focused Treatments
While treating the underlying cause is most important, some people also seek cosmetic improvement of the skin itself. A dermatologist may recommend certain topical creams or treatments to help lighten the affected areas. These include retinoid creams, alpha hydroxy acid lotions, or prescription exfoliants.
However, these treatments only improve the appearance of the skin. They do not fix the underlying cause of acanthosis nigricans. For this reason, they are usually used alongside medical treatment, not instead of it.
Lifestyle Changes That Help
Healthy lifestyle habits play a major role in managing this condition. In addition to helping with weight and blood sugar, regular physical activity improves insulin sensitivity throughout the body. Even a daily 30-minute walk can make a meaningful difference over time.
Eating a diet that is high in fibre and low in refined carbohydrates and sugar is particularly helpful. Foods like vegetables, whole grains, legumes, and lean proteins support healthy blood sugar levels. Many provincial health programmes in Canada offer free or low-cost nutritional counselling — ask your family doctor for a referral.
When to See a Doctor
You should see a doctor if you notice dark, thick, or velvety patches of skin appearing on your body — especially if they develop quickly or are spreading. Acanthosis nigricans that appears suddenly can sometimes be a sign of a more serious condition.
Book an appointment with your family doctor if you notice these skin changes, particularly if you also have a family history of diabetes or if you are experiencing other symptoms like increased thirst, fatigue, or unexplained weight gain.
If you do not have a family doctor, a walk-in clinic is a good first step. Most walk-in clinics across Canada can order basic blood tests and refer you to the appropriate specialist. You can also contact your provincial health line — such as Health811 in Ontario or 811 in British Columbia — for guidance on your next steps.
Do not wait to seek care simply because the skin changes do not hurt. Early detection of insulin resistance or diabetes makes a big difference in long-term health outcomes. As always, speak with a qualified healthcare professional before making any changes to your health routine or treatment plan.
Frequently Asked Questions About Acanthosis Nigricans
Is acanthosis nigricans dangerous?
Acanthosis nigricans itself is not dangerous, but it is often a warning sign of an underlying condition like insulin resistance or type 2 diabetes. Getting checked early can help prevent more serious health problems down the road. Always speak with your family doctor if you notice unexplained skin changes.
Can acanthosis nigricans go away on its own?
Acanthosis nigricans can improve or even disappear when the underlying cause is successfully treated. For example, if insulin resistance improves through weight loss and lifestyle changes, the dark skin patches often fade over time. However, the skin may not return completely to its previous colour in all cases.
Is acanthosis nigricans contagious?
No, acanthosis nigricans is not contagious at all. You cannot catch it from another person or spread it through skin contact. It is a skin response to internal changes in your body, such as high insulin levels or hormonal imbalances.
What does acanthosis nigricans look like?
Acanthosis nigricans appears as dark brown or black patches of skin that feel thick, rough, and velvety to the touch. These patches most commonly appear on the neck, armpits, and groin. The affected skin may also have a slight odour due to moisture building up in the skin folds.
Can children get acanthosis nigricans?
Yes, children can develop acanthosis nigricans, and it is becoming more common as childhood obesity and insulin resistance rates rise in Canada. If a child has dark patches on the neck or armpits, a paediatrician should evaluate them for blood sugar issues. Early intervention can greatly reduce health risks later in life.
How is acanthosis nigricans treated in Canada?
In Canada, treatment for acanthosis nigricans focuses on addressing the underlying cause, such as managing blood sugar through lifestyle changes or medication. Your family doctor can order blood tests and refer you to specialists like an endocrinologist or dermatologist under your provincial health plan. Skin-focused treatments like topical creams may also be recommended by a dermatologist to improve appearance.
Key Takeaways
Acanthosis nigricans causes dark, thick, velvety skin patches, most often on the neck, armpits, and groin.
It is usually a sign of an underlying condition, most commonly insulin resistance or type 2 diabetes.
Other causes include obesity, hormonal disorders, certain medications, and genetics.
Treatment focuses on addressing the root cause — the skin often improves when the underlying issue is treated.
Healthy lifestyle habits, including a high-fibre diet and regular exercise, play a key role in managing this condition.
See your family doctor or a walk-in clinic if you notice unexplained dark skin patches, especially if they appear suddenly.
Provincial health plans in Canada cover most diagnostic tests needed to identify the cause of acanthosis nigricans.
For more information, visit Healthline’s guide to acanthosis nigricans or speak with a healthcare provider who can give you personalized advice based on your health history.
