Dark neck (acanthosis nigricans) and what it says about your health

Key takeaways

• Acanthosis nigricans is thickened, darker, velvety skin in folds such as the neck, underarms and groin.
• The commonest cause is insulin resistance, which is very common in Indians, even at modest body weight.
• It is a risk marker for diabetes, so it deserves a blood test, not just a cream.
• Scrubbing does not remove it and often makes it worse.
• Treating the cause comes first. Creams, peels and lasers can improve the look afterwards.

Is my dark neck just dirt or tanning?

I have seen teenagers whose mothers scrub their necks every day, convinced it is dirt. It is not their fault, and it is not poor hygiene. See, what happens is, acanthosis nigricans is a change in the skin itself. The NHS describes patches that are darker and thicker than usual, dry, and velvety to touch, most often in skin folds such as the neck, armpits and groin. Small skin tags often grow on top.

Tan is different. A tan sits on sun-exposed skin, fades with time and sun protection, and the skin feels normal. Acanthosis nigricans sits in folds, including the back of the neck under the hair, and feels thicker, like velvet.

Why does it happen?

DermNet explains that it is mainly linked to insulin resistance. When the body's cells do not respond well to insulin, the pancreas makes more of it. High insulin levels are thought to stimulate skin cells to grow, and the folds thicken and darken.

The common associations: - Excess weight, especially around the waist. - Prediabetes and type 2 diabetes. - PCOS in women, which often comes with insulin resistance. The NHS now also refers to this as PMOS. - Thyroid and other hormone conditions, less commonly. - Certain medicines, such as oral steroids, some hormone treatments including the contraceptive pill, and insulin injections at the injection site. - Family tendency. The NHS notes it can occur in otherwise healthy people and is more common in black or brown skin.

That is very important to understand for Indians. Many of us carry more fat inside the abdomen and develop insulin resistance at a lower body weight than Western populations. So I do not dismiss a dark neck just because someone "is not that heavy". My weight-loss article on thin outside, fat inside explains this pattern.

When is it a warning sign of something serious?

Rarely, acanthosis nigricans is linked to an internal cancer, most often of the stomach. DermNet lists the warning signs: sudden onset in someone without the usual risk factors, such as a middle-aged person who is not overweight, involvement of the mouth or other moist surfaces, itch, and thick, ridged palms. If that describes you, please see a doctor promptly. This is uncommon, but it should not be missed.

What tests should I get?

The NHS advice is simple: new dark patches need checking because they can be a sign of an underlying condition. What I usually consider, depending on your history:

I only order the ones that will change what we do. Tests are charged at actual cost.

How is it treated?

The cause is the treatment. DermNet calls treating the underlying cause the mainstay. The NHS notes the patches usually fade once the cause is addressed. In practice that means: 1. Food: fewer refined carbohydrates and sugary drinks, more protein such as dal, paneer, curd, eggs, chana and sprouts, and more fibre. 2. Movement: regular walking plus some strength training, which improves how muscles use sugar. 3. Sleep and stress, both of which affect blood sugar. 4. Medicines where needed. DermNet notes that metformin can moderately improve acanthosis nigricans. For some people with significant weight-related insulin resistance, medical weight management may be discussed. These are prescription decisions made after assessment. Our weight loss programme explains how that works. 5. Review of current medicines if one may be contributing. Never stop a prescribed medicine on your own.

Then the skin. Once the cause is being treated, options to improve appearance include: - Topical retinoids such as adapalene or tretinoin - Keratolytics such as salicylic, glycolic or lactic acid, which soften the thickened layer - Mild chemical peels in selected cases - Certain lasers, reported in the medical literature for resistant cases

DermNet lists all of these. They work better, and last longer, when insulin resistance is improving.

How long does it take to fade?

Normally it fades gradually over months as weight, sugar and insulin improve. Skin treatment speeds up the visible change. If the metabolic cause comes back, the darkening often comes back too. That is why I think of the skin as a useful report card for your metabolism. If your neck starts darkening again, it is worth rechecking your sugar.

How we approach this at Dr Tvacha

Under the Second Layer Skin Plan at our Thane, Andheri, Bandra and Dahisar centres, I treat a dark neck as a skin question and a health question together. I examine the skin, order only the tests that matter, and explain the results in plain words. If insulin resistance is the driver, we discuss lifestyle and, where appropriate, medical weight management. Any skin treatment is quoted in writing before you start. For underarm darkening, see dark underarms, and for the small growths that often appear alongside, see skin tags.

Written by

Dr Amit KarkhanisAesthetic Physician · MBBS, Dip. Dermatology (UK) · Reg. No. 2001/02/1124

Founder of Dr Tvacha, practising in Thane since 2005. Leads the weight loss and hair programmes.