Acanthosis Nigricans

Overview

Acanthosis nigricans is a skin condition that causes dark, thick, velvety patches, most often on the neck, armpits, or groin. The skin may look dirty but it is not dirt — it is a change in the skin itself. It is often a sign that the body has too much insulin in the blood, which can be linked to type 2 diabetes or other hormonal problems.

Yes, acanthosis nigricans is fairly common, especially in people who have obesity or who have a family history of type 2 diabetes. It is also more common in people with darker skin tones, though it can happen in anyone.

It can affect children, teens, and adults. It is more likely in people who are overweight, have polycystic ovary syndrome (PCOS), or have a close family member with diabetes. Rarely, it can occur as a sign of certain cancers, but this is very uncommon.

Symptoms

Common symptoms

• Dark, thick, velvety patches of skin that may feel soft to the touch
• Patches most often appear on the back and sides of the neck, in the armpits, or in the groin
• Patches may also appear on the elbows, knees, knuckles, or under the breasts
• The skin may look gray, brown, or black and can feel dry or slightly rougher than usual
• Sometimes mild itching, but often there is no discomfort at all

Symptoms in children

• The same dark, velvety patches on the neck, armpits, or groin
• Having a child with acanthosis nigricans often suggests that they may be at higher risk for developing type 2 diabetes later in life
• Children with the condition may also have dark patches on their forehead or around the mouth

Symptoms in older adults

• The patches look the same as in younger people
• In older adults, acanthosis nigricans is more often linked to weight gain or diabetes, but a sudden appearance may also require checking for other health problems
• Skin can be more fragile with age, so rubbing or scratching should be avoided

Causes

Main causes

• Insulin resistance — when your body's cells don't respond normally to insulin, the body makes more insulin, which can cause skin cells to grow and produce extra pigment
• Hormone changes — conditions like polycystic ovary syndrome (PCOS) or problems with the thyroid or adrenal glands
• Certain medications — for example, high doses of niacin, some birth control pills, or some medicines used to treat other conditions
• Rarely, changes in the skin can be a sign of a tumor in the stomach or another organ (this is very rare)

Risk factors

• Being overweight or having obesity
• A family history of type 2 diabetes or acanthosis nigricans
• Having been diagnosed with prediabetes or type 2 diabetes
• Having polycystic ovary syndrome (PCOS) or other hormonal disorders
• Having darker skin tone, though people of all skin types can get it
• Rarely, using certain hormone treatments or medicines

When to see a doctor

See a doctor urgently if:

• If the dark patches appear very quickly or spread rapidly
• If you also have unintentional weight loss, fever, or extreme tiredness
• If you have signs of very high blood sugar, such as excessive thirst, frequent urination, or feeling sick

Book a routine appointment if:

• See a doctor if you notice a new or changing area of dark, thick skin anywhere on your body
• If you already know you have diabetes or prediabetes and you notice skin changes, mention it at your next appointment
• If the patches are itchy, sore, or are affecting your self-confidence, talk to a doctor about what can help

Diagnosis

A doctor can usually diagnose acanthosis nigricans just by looking at your skin. They will also ask about your medical history, your family history, any medicines you take, and other health conditions you may have.

Tests that may be done

• A blood test to check your blood sugar (glucose) level
• A test to see how well your body handles sugar (oral glucose tolerance test) — this involves drinking a sugary drink and having blood taken over a few hours
• An insulin level test to check for insulin resistance
• Sometimes a thyroid test or a test for other hormones if the doctor suspects a hormonal condition
• In rare cases, a small skin sample (biopsy) is needed, but this is only done if the diagnosis is unclear

What to expect at your appointment

The doctor will examine the affected areas and likely ask you to have a simple blood test. You may be asked to fast for several hours before the blood draw, so the doctor will give you clear instructions. The whole process is usually quick and painless. After that, the doctor will talk with you about any results and what you can do next.

Treatment

Treatment for acanthosis nigricans focuses on fixing the underlying cause. For most people, this means improving blood sugar control, losing weight, and getting more physical activity. When the cause is addressed, the skin patches often fade on their own.

Self-care at home

• Keep the affected areas clean and dry to avoid irritation or infection
• Use a gentle moisturizer if the skin feels dry, but avoid harsh scrubs or strong chemicals
• Wear loose clothing to reduce friction and rubbing
• Eat a balanced diet made mostly of vegetables, fruits, whole grains, and lean proteins
• Aim to move your body regularly — even a daily 30-minute walk can help
• If you are overweight, try to lose weight gradually with the support of a health professional

Medical treatments

Doctors may prescribe creams or ointments to help soften and lighten the skin, but these treat only the appearance, not the root cause. Sometimes, treating the underlying condition with medicines like metformin or other diabetes medications can help, but any medication must be prescribed by a qualified healthcare provider. There are no specific over-the-counter creams proven to cure acanthosis nigricans, so always ask your doctor or pharmacist for advice.

When is surgery considered?

Surgery is not used to treat acanthosis nigricans itself. In the very rare case that a tumor is causing the skin changes, surgery may be part of the treatment for that tumor, but this is uncommon.

Living with this condition

Living with acanthosis nigricans means caring for your skin gently and paying attention to your overall health. The patches may not disappear overnight, but with time and healthy habits, most people see improvement. Try not to scrub the areas hard, and be patient — skin changes take weeks to months to fade.

Lifestyle tips

• Eat regular meals and choose foods that keep your blood sugar steady, like vegetables, whole grains, and legumes
• Limit sugary drinks and processed snacks
• Try to be active most days of the week — even small amounts help
• Get enough sleep and manage stress, since both affect your blood sugar and hormones
• Quit smoking if you smoke, and avoid secondhand smoke
• Follow up with your doctor for regular check-ups and blood tests as advised

Diet and exercise

A balanced diet and regular exercise are the most powerful tools you have. You don't need to make drastic changes all at once. Start by adding more vegetables to your meals and going for short walks after eating. Over time, aim for at least 150 minutes of moderate exercise per week. This doesn't have to be intense — brisk walking, swimming, or cycling all count. If you are not sure what diet is right for you, ask a doctor or a registered dietitian.

Mental health and emotional wellbeing

Seeing dark patches on your skin can feel upsetting, and you might feel self-conscious or worried. That is completely normal. Your skin does not define you, and many people have this condition. Talking to a friend, family member, or counselor can help. If you often feel sad, anxious, or hopeless, please reach out for support.

Prevention

You may be able to prevent acanthosis nigricans by keeping your weight in a healthy range, staying active, and eating a balanced diet. For some people, there is also a genetic tendency, but healthy lifestyle habits still make a very big difference.

Screening programmes

If you have risk factors like obesity, a family history of diabetes, or PCOS, ask your doctor about having a blood test for prediabetes or type 2 diabetes. Finding these conditions early gives you a much better chance of preventing complications.

Complications

If left untreated

• Higher risk of developing type 2 diabetes, because acanthosis nigricans is often a sign of insulin resistance
• The skin changes may become darker, thicker, and harder to treat if the underlying cause is not addressed
• Increased risk of other metabolic problems, such as high cholesterol and high blood pressure
• If caused by an underlying hormonal problem, that condition may also progress without treatment

Long-term outlook

The outlook is generally very positive. For most people, acanthosis nigricans improves or completely goes away when the underlying cause is treated. With weight loss, physical activity, and blood sugar control, the skin often clears up. Even if the patches stay, they are not harmful to your health. The most important thing is to work with your healthcare team to take care of your overall wellbeing.

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