Acanthosis Nigricans: Causes, Signs, and Treatment

You've been told your skin is just dry. You've tried every exfoliating scrub and moisturizer on the shelf. But those dark, velvety patches on your neck, underarms, or groin aren't budging. They're thickening. And no one seems to be asking why your skin is doing this in the first place.

Key Takeaways

• Acanthosis nigricans is a skin marker of insulin resistance, not a hygiene issue.
• Dark, velvety patches appear in body folds due to excess insulin driving skin cell growth.
• It's most common in people with obesity, prediabetes, or type 2 diabetes.
• Malignant acanthosis nigricans is rare but signals internal cancer, usually gastric adenocarcinoma.
• Treatment focuses on addressing the underlying metabolic or hormonal driver, not just the skin.
• Topical treatments may lighten patches but won't resolve the condition without systemic intervention.

What Acanthosis Nigricans Actually Is (and What Drives It)

Acanthosis nigricans is a skin condition characterized by dark, thickened, velvety patches that typically appear in body folds like the neck, armpits, groin, and knuckles. It's not a rash. It's not dirt. It's a visible sign that something deeper is happening at the metabolic or hormonal level. The skin changes occur because elevated insulin levels, or insulin-like growth factors, bind to receptors on skin cells and trigger rapid proliferation of keratinocytes and fibroblasts. The result is hyperpigmentation and a thickened, textured appearance that doesn't respond to scrubbing or standard skincare.

The most common form, benign acanthosis nigricans, is strongly associated with insulin resistance. When cells become less responsive to insulin, the pancreas compensates by producing more. This excess insulin doesn't just affect glucose metabolism. It also stimulates skin cell growth, particularly in areas where skin rubs against skin.

The condition is most prevalent in people with obesity, prediabetes, or type 2 diabetes, and it often appears before blood sugar levels become overtly abnormal. In children and adolescents, acanthosis nigricans on face or neck can be an early warning sign of metabolic dysfunction that warrants further investigation.

How Acanthosis Nigricans Connects to Hormones, the Gut, and Immune Function

Endocrine system connections

Acanthosis nigricans reflects systemic processes that extend well beyond the skin. Elevated insulin and insulin-like growth factor-1 (IGF-1) drive the skin changes, but the underlying cause is often broader metabolic dysregulation. Conditions like polycystic ovary syndrome (PCOS), Cushing's syndrome, and hypothyroidism can all present with acanthosis nigricans because they alter hormone signaling in ways that promote insulin resistance or directly stimulate skin cell proliferation.

The gut-skin axis

Emerging research suggests that gut microbiome composition and intestinal permeability may influence systemic inflammation and insulin sensitivity, both of which can manifest as skin changes. Chronic low-grade inflammation driven by gut dysbiosis or increased intestinal permeability may amplify the metabolic signals that lead to acanthosis nigricans. This is why addressing diet, gut health, and metabolic markers often improves the skin condition more effectively than topical acanthosis nigricans treatments alone.

What Drives Flares and Severity (and Why Some Cases Progress Faster)

The severity of acanthosis nigricans is largely determined by the degree of insulin resistance and the duration of metabolic dysfunction. Several factors accelerate progression:

• Weight gain, particularly visceral fat accumulation, worsens insulin resistance and accelerates skin changes.
• High glycemic diets spike blood sugar and insulin levels repeatedly throughout the day.
• Certain medications, including systemic corticosteroids, oral contraceptives, and niacin, can induce or worsen the condition by altering insulin sensitivity or hormone levels.

Hormonal fluctuations during puberty, pregnancy, or menopause can also trigger or exacerbate the condition. Androgens, in particular, increase sebum production and may amplify insulin's effects on skin cells. This is why acanthosis nigricans is common in adolescents with PCOS and in individuals with hyperandrogenism. Stress, through its effects on cortisol and the hypothalamic-pituitary-adrenal (HPA) axis, can further impair insulin sensitivity and worsen skin manifestations.

Why the Same Condition Looks Different (and Responds Differently) in Different People

Not everyone with insulin resistance develops acanthosis nigricans, and not everyone with the condition has the same presentation. Genetics play a significant role. Certain populations, including individuals of African, Hispanic, Native American, and South Asian descent, have higher rates of both insulin resistance and acanthosis nigricans. Skin type and melanin content also influence how visible the hyperpigmentation appears. In individuals with lighter skin tones, the darkening may be less pronounced, leading to delayed recognition or misdiagnosis.

The distribution and severity of skin changes also vary. Some people develop isolated patches on the neck or underarms, while others have widespread involvement across multiple body folds. The degree of skin thickening and texture change depends on how long the condition has been present and how aggressively the underlying metabolic dysfunction is progressing.

When Skin Symptoms Point to Something Systemic

While most cases of acanthosis nigricans are benign and metabolic in origin, a small subset is associated with internal malignancy. Malignant acanthosis nigricans is a paraneoplastic syndrome, most commonly linked to gastric adenocarcinoma, though it has also been reported with cancers of the pancreas, ovary, liver, lung, and other organs. This form tends to appear suddenly, progress rapidly, and involve more extensive areas, including the palms, soles, and oral mucosa. It often occurs in individuals without obesity or metabolic risk factors, which should raise clinical suspicion.

Malignant acanthosis nigricans treatments focus on addressing the underlying cancer, as the skin changes often improve with successful tumor management. However, the prognosis is generally poor because the condition typically presents in advanced stages of malignancy. Any new-onset acanthosis nigricans in an adult without clear metabolic risk factors, or any rapidly progressive case, warrants a thorough workup for occult malignancy.

Beyond cancer, acanthosis nigricans can signal other systemic conditions. It's been associated with autoimmune disorders, including systemic lupus erythematosus and scleroderma, as well as with certain genetic syndromes that affect insulin signaling. In children, the sudden appearance of acanthosis nigricans should prompt evaluation for endocrine disorders, including growth hormone excess, Cushing's syndrome, or congenital lipodystrophy.

What Biomarkers Can Tell You When Topicals Aren't Enough

If you have acanthosis nigricans, the skin is telling you something about what's happening inside. The most relevant biomarkers to assess are those that reflect insulin sensitivity and metabolic health:

• Fasting glucose and hemoglobin A1c provide a snapshot of blood sugar control, but they often remain normal until insulin resistance is advanced.
• Fasting insulin and the HOMA-IR (homeostatic model assessment of insulin resistance) are more sensitive early markers of pancreatic compensation.
• Lipid panels, including triglycerides, HDL cholesterol, and apolipoprotein B, help assess cardiovascular risk.
• High-sensitivity C-reactive protein (hs-CRP) reflects systemic inflammation, which both drives and is driven by metabolic dysfunction.

In women with suspected PCOS, measuring total testosterone, free testosterone, DHEA-S, and sex hormone-binding globulin (SHBG) can clarify the hormonal contribution. For individuals with rapid onset or atypical presentations, additional workup may include thyroid function tests, cortisol levels, and screening for malignancy. Tracking these markers over time, not just reacting to individual flares, is more likely to identify the underlying driver and guide effective intervention.

Getting to the Root of What's Driving Your Skin

Acanthosis nigricans isn't a cosmetic problem. It's a metabolic signal. If your skin is darkening and thickening despite topical interventions, Superpower's biomarker panel can show you what's happening at the insulin, hormone, and inflammation level. Measuring fasting insulin, glucose, A1c, lipids, and inflammatory markers gives you a clearer picture of what's driving the skin changes and what needs to change systemically to reverse them.