Acanthosis Nigricans

Overview

Acanthosis nigricans is a skin condition characterized by dark, velvety discoloration and thickening in the body's skin folds and creases. The neck, armpits, and groin are the most commonly affected areas, though the elbows, knees, knuckles, and lips can also be involved. The skin takes on a darker tone — ranging from light brown to nearly black — and feels noticeably thicker and rougher to the touch, resembling velvet. Some individuals may notice mild itching or an unusual odor in the affected areas.

Acanthosis nigricans is not a disease in itself but rather a skin sign that points to an underlying process in the body. It is most commonly associated with insulin resistance, making it particularly prevalent in people at risk for type 2 diabetes, those with obesity, and women with polycystic ovary syndrome (PCOS). Certain medications, rare genetic syndromes, and — very rarely — internal organ cancers can also cause this skin change.

The condition can occur at any age and in any skin tone, though it tends to be more visually pronounced in individuals with darker complexions. Its prevalence is rising, largely in parallel with the global increase in obesity and insulin resistance.

Acanthosis nigricans itself is neither harmful nor contagious. However, identifying and addressing the underlying cause is essential. When the root cause is treated effectively, the skin changes often improve or resolve entirely.

Symptoms

The symptoms of acanthosis nigricans typically develop gradually and may go unnoticed in the early stages. Skin changes can progress slowly over months or years.

Acanthosis nigricans symptoms include the following:

• Darkening of the skin. The affected area appears noticeably darker than the surrounding skin. The discoloration can range from light tan to deep brown or near-black. This change is often mistaken for dirt, but unlike dirt, it does not wash away.
• Velvety skin texture. The affected skin feels thick, rough, and distinctly velvety to the touch — noticeably different from the surrounding normal skin.
• Involvement of skin folds. Changes most often appear on the back and sides of the neck, the armpits, and the groin. The elbows, knees, navel area, knuckles, and lips are less commonly affected.
• Skin tags. Small, soft, flesh-colored growths on stalks (fibroepithelial polyps) may develop in or around the affected areas. These are harmless but may be cosmetically bothersome.
• Mild itching or odor. Some individuals experience mild itching in the affected areas. In deep skin folds where moisture accumulates, an unusual odor may occasionally develop.
• Symmetrical distribution. Changes tend to appear symmetrically on both sides of the body — for example, both sides of the neck or both armpits are typically affected simultaneously.

The severity of symptoms varies considerably between individuals. Some people notice only subtle discoloration, while others develop extensive thickening across large areas. Depending on the underlying cause, changes may develop rapidly or progress slowly over many years.

When to See a Doctor

Acanthosis nigricans is generally not a medical emergency, but it is an important finding that warrants evaluation by a physician. If the underlying cause goes unidentified and untreated, it can lead to serious health consequences.

Seek medical evaluation if:

• You notice dark, velvety skin changes on your neck, armpits, or groin
• The skin discoloration does not improve with washing
• The changes appeared suddenly or progressed rapidly over weeks to months — this may signal a serious underlying condition
• You have a family history of diabetes, or you experience symptoms such as excessive thirst, frequent urination, or unusual fatigue
• Your child has developed this type of skin change
• The skin changes are accompanied by weight gain, irregular periods, or increased hair growth
• The affected area is expanding rapidly, becoming painful, or changing in character

Rapidly developing acanthosis nigricans in particular warrants investigation for an underlying malignancy. For this reason, these skin changes should never be dismissed as purely cosmetic and always merit professional evaluation.

Causes

Acanthosis nigricans can have several underlying causes. Insulin resistance is the most common, but a number of other conditions and factors are also associated with this skin change.

Possible causes of acanthosis nigricans include the following:

• Insulin resistance and type 2 diabetes. This is the most common underlying cause. When the body's cells do not respond adequately to insulin, the pancreas compensates by producing more. Elevated circulating insulin levels stimulate skin cells to proliferate, producing the characteristic changes of acanthosis nigricans. Insulin resistance is strongly associated with obesity and can be an early warning sign of type 2 diabetes.
• Obesity. Excess body weight is one of the most significant drivers of insulin resistance. This creates a strong link between obesity and acanthosis nigricans. Because weight loss reduces insulin resistance, managing body weight plays both a preventive and therapeutic role in obesity-related cases.
• Polycystic ovary syndrome (PCOS). Insulin resistance is common in PCOS. Women with this condition frequently develop acanthosis nigricans alongside other features such as irregular menstrual cycles, excess hair growth, and weight gain.
• Medications. Certain medications can trigger acanthosis nigricans, including high-dose nicotinic acid (niacin), corticosteroids, oral contraceptives, and some antipsychotic medications. In medication-related cases, the skin changes typically improve after the offending drug is discontinued or changed.
• Genetic (familial) causes. In some individuals, acanthosis nigricans occurs in the absence of any underlying disease and runs in families. This type usually appears in childhood, may fade over time, and is not associated with significant health concerns.
• Hormonal disorders. Conditions such as thyroid disease, Cushing's syndrome (excess cortisol), and acromegaly (excess growth hormone) can also be associated with acanthosis nigricans.
• Internal malignancies (paraneoplastic acanthosis nigricans). Rarely, rapidly developing or widespread acanthosis nigricans — particularly in adults — may be associated with an underlying cancer, most often of the stomach, liver, colon, or ovary. This form typically appears abruptly and may be more extensive than the metabolic variety.

Risk Factors

Several factors are associated with an increased likelihood of developing acanthosis nigricans:

• Obesity. A high body mass index is one of the strongest risk factors, as excess weight — particularly abdominal adiposity — promotes insulin resistance.
• Family history of diabetes. Having a first-degree relative with type 2 diabetes increases the risk of developing insulin resistance and, in turn, acanthosis nigricans.
• Ethnicity. Acanthosis nigricans is more prevalent among Black, Hispanic, Native American, and South Asian individuals. This difference is thought to reflect both genetic predisposition and differences in insulin resistance susceptibility.
• Polycystic ovary syndrome. Due to the high prevalence of insulin resistance in PCOS, women with this condition face an elevated risk.
• Type 2 diabetes or prediabetes. Individuals with existing blood sugar dysregulation have a higher likelihood of developing this skin finding.
• Certain medications. Long-term use of corticosteroids, high-dose niacin, and some hormonal medications increases risk.

Diagnosis

Acanthosis nigricans is typically diagnosed through clinical examination — the skin findings are usually distinctive enough to identify visually. However, identifying the underlying cause requires additional testing, which is the most important part of the diagnostic process.

Diagnostic methods include the following:

• Physical examination and medical history. The physician evaluates the skin changes — noting color, texture, distribution, and extent — and asks about the onset and progression of the changes, current medications, weight history, family history, and any accompanying symptoms such as menstrual irregularities or fatigue.
• Blood glucose and insulin testing. Fasting blood glucose, HbA1c (a measure of average blood sugar over the past three months), and fasting insulin levels are measured. These tests reveal the presence of insulin resistance, prediabetes, or type 2 diabetes. The HOMA-IR index can be calculated to quantify the degree of insulin resistance.
• Complete blood count and metabolic panel. Liver and kidney function, electrolytes, and thyroid hormone levels are assessed to evaluate general health and screen for potential hormonal causes.
• Hormonal testing. If PCOS is suspected, androgenic hormones (testosterone, DHEA-S) may be measured. Cortisol levels are checked if Cushing's syndrome is a concern.
• Lipid profile. Cholesterol and triglyceride levels are measured, as dyslipidemia frequently accompanies insulin resistance and metabolic syndrome.
• Skin biopsy. In rare cases, a small skin sample may be examined under a microscope to confirm the diagnosis or rule out other skin conditions. This is not routinely required.
• Cancer screening. In cases with rapid onset, unusual distribution, or atypical features, imaging studies and additional tests may be ordered to investigate the possibility of an underlying malignancy.

Treatment

The primary goal of treatment is to identify and address the underlying cause. When the root condition is effectively managed, the skin changes of acanthosis nigricans typically improve on their own. Treatments targeting the skin changes directly are primarily cosmetic in nature.

Treatment options include the following:

• Weight management. In obesity-related cases, weight loss is the most effective intervention. Losing even 5–10 percent of body weight can meaningfully reduce insulin resistance and lead to noticeable improvement in skin appearance. Regular physical activity and a healthy diet are the cornerstones of this approach.
• Treatment of insulin resistance. Insulin-sensitizing medications such as metformin reduce insulin resistance and are used in the management of type 2 diabetes, prediabetes, and PCOS. As insulin resistance improves, skin findings often regress.
• Treatment of the underlying condition. Addressing the specific cause — whether PCOS, thyroid disease, Cushing's syndrome, or a medication side effect — typically leads to improvement in acanthosis nigricans. If a medication is identified as the cause, switching to an alternative agent is usually recommended.
• Topical treatments. To improve the cosmetic appearance of the skin, topical agents such as retinoids (tretinoin), alpha-hydroxy acid lotions, and skin-lightening preparations may be used. These can soften the skin texture and reduce discoloration but do not treat the underlying cause.
• Dermatological procedures. Laser therapy and chemical peels may improve skin appearance in some patients and are used for cosmetic purposes. Results vary between individuals.
• Dietary modifications. A diet low in refined carbohydrates, added sugars, and processed foods — and rich in vegetables, fiber, lean protein, and healthy fats — supports insulin sensitivity. The Mediterranean dietary pattern is often recommended for this purpose.
• Skin care. Keeping affected areas clean and dry, using gentle fragrance-free moisturizers, and protecting skin folds from friction can improve comfort and reduce the risk of secondary infections.

Complications

Acanthosis nigricans itself does not directly cause serious complications. However, it frequently signals underlying conditions that, if left untreated, can lead to significant health consequences.

• Development of type 2 diabetes. In individuals with insulin resistance-related acanthosis nigricans, the risk of progressing to type 2 diabetes is substantial if the underlying condition is not addressed. The skin finding can therefore serve as a valuable early warning sign.
• Cardiovascular disease. Insulin resistance and obesity increase the risk of high blood pressure, dyslipidemia, and cardiovascular disease. Acanthosis nigricans may be one manifestation of this broader risk profile.
• Metabolic syndrome. The cluster of obesity, insulin resistance, elevated blood pressure, and lipid abnormalities — collectively known as metabolic syndrome — frequently coexists with acanthosis nigricans and carries long-term risks for heart disease and stroke.
• Psychological and social impact. Visible skin changes — particularly on the neck and underarms — can lead to self-consciousness, reduced self-esteem, social withdrawal, and anxiety. Children and adolescents are especially vulnerable to these psychosocial effects.
• Skin infections. Moisture accumulation in the deep skin folds affected by acanthosis nigricans can predispose to fungal or bacterial skin infections.
• Delayed cancer diagnosis. In cases of rapidly developing acanthosis nigricans where a paraneoplastic cause is not considered, an underlying malignancy may be diagnosed late. Recognizing atypical presentations and investigating promptly is therefore essential.

Living with Acanthosis Nigricans

A diagnosis of acanthosis nigricans can feel discouraging, but with the right treatment and lifestyle changes, both the skin findings and their underlying causes can be effectively managed. Most people see meaningful improvement once the root condition is addressed.

Nutrition and Weight Management

Adopting an eating pattern that targets insulin resistance benefits both the skin and overall health. Limit foods with a high glycemic index — including sugar, white bread, white rice, and ultra-processed products. Prioritize vegetables, legumes, whole grains, fish, and olive oil. Avoid skipping meals; smaller, regular meals help prevent blood sugar spikes. Replace sugary beverages with water as a default.

Physical Activity

Regular exercise is one of the most powerful tools for improving insulin sensitivity. Aim for at least 150 minutes of moderate-intensity aerobic activity per week — such as brisk walking, cycling, or swimming. Adding two to three sessions of resistance training per week further enhances insulin sensitivity. Small daily changes — taking the stairs, walking instead of driving short distances — also contribute meaningfully over time.

Skin Care

Gently cleanse affected areas daily without scrubbing harshly. Keep skin folds dry to prevent moisture buildup. Fragrance-free, gentle moisturizers can help soften the skin. Avoid harsh soaps and products containing strong chemical irritants. If you notice signs of a fungal or bacterial infection — such as increasing redness, itching, or odor — consult your doctor promptly.

Psychological Support

Skin changes in visible areas can affect self-image and confidence. It helps to know that acanthosis nigricans is a very common finding — you are not alone. If the psychological impact is significant, speaking with a psychologist or counselor can be valuable. For children and adolescents, a supportive and matter-of-fact approach from family members makes a meaningful difference.

Regular Monitoring

Blood glucose, insulin levels, and other metabolic markers should be monitored at regular intervals as recommended by your doctor. Track any changes in your skin findings and report rapid progression, new areas of involvement, or pain. A comprehensive metabolic panel at least once a year helps assess treatment response and catch any emerging issues early.

Preparing for Your Appointment

Coming prepared to your appointment helps your doctor reach an accurate diagnosis more efficiently and identify the underlying cause without delay.

What you can do:

• Note when you first noticed the skin changes and how quickly they developed
• Identify which areas are affected and take photos if possible
• Record any recent changes in your weight
• List all medications, vitamins, and supplements you currently take
• Mention any family history of diabetes, obesity, or hormonal conditions
• Note any accompanying symptoms such as irregular periods, increased hair growth, fatigue, or excessive thirst
• Write down your questions in advance

Questions you may wish to ask your doctor:

• What is most likely causing this skin change?
• Do I have insulin resistance or diabetes?
• What tests do I need?
• Will losing weight improve the skin findings?
• What dietary changes do you recommend?
• Is medication needed?
• What can be done to improve the skin's appearance?
• How often should I come for follow-up?
• Could this be related to cancer?

Questions your doctor may ask:

• When did the skin changes first appear, and how quickly did they develop?
• Is there a family history of diabetes or insulin resistance?
• Have you gained weight recently?
• Are you taking any regular medications?
• Have you noticed any changes in your menstrual cycle? (for women)
• Do you experience excessive fatigue, thirst, or frequent urination?
• Have you ever been told your blood sugar was elevated?