Quick summary

If you notice the skin on the back of your neck, your armpits, or body folds turning darker, thicker, and velvety, and it does not wash off no matter how hard you scrub, that may be acanthosis nigricans. For women with PCOS, this skin change is not just a cosmetic issue. It is one of the clearest visible clues that the body is struggling with insulin resistance. This guide is written for Malaysian women, informed by the 2023 international PCOS guidelines, Malaysian Ministry of Health resources, and National Pharmaceutical Regulatory Agency (NPRA) safety checks where supplements are involved.

What is acanthosis nigricans?

Acanthosis nigricans is a change in the skin where certain areas become:

  • Darker than the surrounding skin, usually brown to almost black
  • Rough and thickened, with a velvety texture when touched
  • Not itchy and not painful in most cases, although dark folds can sometimes feel damp or have an odour

The most commonly affected spots are the back and sides of the neck, the armpits, the groin folds, and sometimes the knuckles, elbows, or knees. In women with darker skin tones, including many Malaysian women, the change can be more noticeable and appear in more places, including the face. Many people first mistake it for “dirt” or unwashed skin and scrub it with a rough towel, pumice stone, or skin-whitening products. Unfortunately this does not help and can injure the skin, because the darkening comes from within, not from the surface.

Another sign that often appears alongside acanthosis nigricans is skin tags (acrochordons), small soft growths that hang from the skin, especially around the neck and armpits. Having both at once is a strong hint that insulin resistance may be involved.

Why acanthosis nigricans appears in PCOS

To understand the link, we need to understand what happens behind the scenes. In many women with PCOS, the body’s cells become less responsive to insulin, the hormone that helps glucose enter cells. When cells behave “stubbornly” like this, the pancreas must release more insulin to achieve the same effect. This is called hyperinsulinaemia, meaning high insulin levels in the blood.

This excess insulin does more than manage glucose. When its level is too high, insulin starts binding to IGF-1 growth-factor receptors found on skin cells, namely keratinocytes and fibroblasts. This stimulation makes these skin cells multiply faster and thicken, producing the dark velvety patches we see. In short: acanthosis nigricans in women with PCOS is usually insulin resistance showing up on the skin. This is why doctors treat it as a clinical marker, not just a beauty concern.

Understanding this link matters because it changes how you treat it. If you only target the skin, you are treating the smoke; if you target insulin resistance, you put out the fire.

What the research says: treating the cause

Medical evidence consistently shows that the most effective treatment for acanthosis nigricans is treating the underlying condition, namely insulin resistance and excess weight, rather than creams alone. Here is the evidence by strength.

Weight loss and lifestyle management (strong evidence). Because most cases of acanthosis nigricans are linked to excess weight and high insulin, gradual weight loss is considered first-line. As insulin sensitivity improves, the dark patches usually lighten and thin out over time. Regular physical activity, even brisk walking, helps muscles absorb glucose without much insulin, lowering the insulin burden on the skin.

Metformin (moderate to strong evidence for insulin resistance). Metformin improves insulin sensitivity and lowers insulin levels. By targeting the metabolic cause, it can help reduce acanthosis nigricans in some women, alongside its benefits for PCOS cycles and metabolism. Metformin is a prescription medicine, so the decision to start it must be made with a doctor.

Berberine (moderate evidence, still limited compared with metformin). Berberine is a natural compound that also acts on the AMPK pathway like metformin, and several randomised trials show it improves insulin resistance and lipid profiles in women with PCOS, sometimes comparable to metformin in the short term. However, the evidence is smaller and shorter than for metformin, and it is not a registered medicine for PCOS. Important: berberine should not be taken during pregnancy or breastfeeding, it can interact with many medicines (including metformin, blood-pressure drugs, and drugs processed by the liver), and it can push blood sugar too low if combined with diabetes medication. Always check the product’s registration status at npra.gov.my and speak to a doctor or pharmacist first. Any dose mentioned here refers to the dose used in studies, not a prescription.

Vitamin D (limited but reasonable evidence). If you are vitamin D deficient, correcting it may indirectly help insulin sensitivity. Many Malaysian women are deficient despite living in a hot country, due to limited sun exposure and covering clothing. A simple blood test can confirm this.

Topical treatments (creams) for cosmetic purposes (moderate evidence, limited effect). Creams such as topical retinoids (for example tretinoin or adapalene) and urea can gradually thin and lighten the patches by speeding up the shedding of old skin cells. A 2024 systematic review supports using tretinoin and adapalene for this purpose. However, these creams only address the surface; without fixing insulin resistance, the patches usually return. Topical retinoids must not be used during pregnancy. Use them only under the advice of a dermatologist or your doctor.

Practical context and steps for Malaysian women

Here is how to manage acanthosis nigricans within Malaysia’s healthcare setting.

  • Start at a Klinik Kesihatan. You can see a doctor at a government health clinic for RM1 as a citizen, with follow-ups usually around RM5. The doctor can examine the skin (acanthosis nigricans is usually diagnosed clinically, just by looking and touching, rarely needing a biopsy) and refer you for blood tests if needed.
  • Relevant tests. To assess insulin resistance and long-term risk, the doctor may check fasting glucose, HbA1c, fasting insulin, lipid profile, and PCOS hormones. Obvious acanthosis nigricans is a strong reason to screen for type 2 diabetes, because this skin sign often appears before diabetes is confirmed.
  • A PCOS diagnosis does not require a transvaginal ultrasound. For unmarried women, a transabdominal ultrasound (through the abdomen) is first-line in Malaysia, and PCOS can still be diagnosed without a transvaginal scan based on cycle and hormone criteria.
  • Do not try to whiten the skin. Avoid black-market whitening creams, pumice stones, or hard scrubbing. They do not address the cause and can cause wounds, infection, or scarring.
  • Supplement halal status. If you are considering supplements, look for the JAKIM halal logo and check the gelatin source for soft capsules, and confirm the product registration number with NPRA.

Questions to bring to your doctor

Bringing clear questions makes a short consultation more valuable. You can ask:

  • “Is this dark patch a sign of insulin resistance for me, and do I need a glucose or insulin test?”
  • “Do my levels show a risk of type 2 diabetes, and what is my target?”
  • “Is metformin suitable for me, given my cycle and metabolic situation?”
  • “What is a realistic weight-loss target to help my skin and overall health?”
  • “If I want to try a cream to lighten the patches, which one is safe for me?”

Monitoring progress

Acanthosis nigricans does not disappear within a week. As insulin resistance improves, the skin changes happen slowly, often after several months. Give it at least 3 months before judging any approach, and monitor objectively:

  • Periodic photos of the neck or armpit area in the same light and distance each time, not to judge yourself but to see the pattern
  • Waist circumference, which often changes before the number on the scale
  • Follow-up blood tests every 3 to 6 months for fasting insulin, HbA1c, and lipid profile
  • A cycle log, because metabolic improvement often comes together with more regular periods

If the skin patches appear suddenly, spread quickly, or come with unexplained weight loss, see a doctor promptly, because in rare cases acanthosis nigricans can be linked to other more serious problems. For the majority of women with PCOS, however, it is a manageable metabolic signal with the right plan.

Next steps

Acanthosis nigricans is best seen as an invitation to review your overall metabolic health, not just a skin problem. For a more structured action plan based on your situation, whether newly diagnosed, focused on skin symptoms, or managing PCOS long term, see the Quick Start guides covering a range of specific scenarios.