Medically reviewed by Chandre Tina May, Registered Nurse & Menopause Society Certified Practitioner (MSCP). See our editorial policy.
You’ve scrubbed at that dark patch on the back of your neck, wondered if it’s dirt, maybe felt quietly ashamed — and it simply won’t wash away. If you have PCOS, what you’re looking at is almost certainly acanthosis nigricans, and it has nothing to do with cleanliness. It is a real, recognised skin change that is directly connected to how PCOS affects your body’s hormones and metabolism. No one tells women with PCOS this is part of the picture — but it is, and you deserve to understand why.
This article explains the link between PCOS acanthosis nigricans and insulin resistance, what the patches mean for your health, and what you can actually do about them.
What’s Actually Happening in Your Body
Think of your body as a house where insulin is the key that unlocks the front door so glucose (energy) can get inside the cells. In many women with PCOS, the locks are stiff — the cells don’t respond to insulin as well as they should. This is called insulin resistance. The body’s response? Make more keys. The pancreas pumps out extra insulin to try to force the door open.
All that excess insulin circulating in your bloodstream doesn’t just stay in the “energy” hallway — it wanders into other rooms of the house. One of those rooms is your skin. High insulin levels stimulate receptors in skin cells, causing them to multiply faster than normal. The result is a thickening and darkening of the skin, particularly in folds and creases: the back of the neck, armpits, groin, and under the breasts. That is acanthosis nigricans.
According to the NHS, acanthosis nigricans is most commonly associated with insulin resistance, Type 2 diabetes risk, and conditions like PCOS. It is not a rash, not an infection, and not caused by anything you did or didn’t do.
What the Patches Look and Feel Like
Acanthosis nigricans has a very specific appearance. Knowing what to look for helps you recognise it — and describe it clearly to a doctor.
Texture and colour
- The skin feels velvety or slightly rough to the touch, not smooth.
- The colour ranges from tan to dark brown or grey — noticeably darker than the surrounding skin.
- In women with deeper skin tones, the contrast can be striking; in lighter skin tones it may appear more greyish-brown.
Where it appears
- Back of the neck — the most common site, often mistaken for a tan line or a dirty collar.
- Armpits
- Groin and inner thighs
- Under the breasts
- Less commonly: elbows, knuckles, or around the belly button.
The patches are not painful, don’t typically itch, and do not spread like an infection. They can develop gradually over months or years, which is why many women don’t notice them at first.
Why PCOS Makes You More Likely to Have It
Research suggests that a significant proportion of women with PCOS have some degree of insulin resistance — the exact figure varies by population and how it’s measured, but it is widely recognised as one of the most common underlying features of the condition. The Verity PCOS charity notes that insulin resistance is central to many of PCOS’s downstream effects: raised androgen levels, irregular periods, weight changes, and yes — skin changes like acanthosis nigricans.
This is why acanthosis nigricans is considered a visible clue that insulin resistance may be at play, even before blood tests confirm it. If you have PCOS and you’ve noticed these patches, it’s worth telling your GP or specialist — not because it’s dangerous in itself, but because it signals something worth investigating and managing.
It’s also worth knowing that acanthosis nigricans is more common in women with a higher body weight, but it absolutely occurs in women of all body sizes with PCOS. It is not exclusively a weight-related condition.
What It’s Commonly Mistaken For
Women with PCOS acanthosis nigricans are often told — or tell themselves — a range of things that delay understanding:
- “It’s just a tan” — but it doesn’t fade in winter.
- “You need to wash better” — it doesn’t scrub away, and vigorous scrubbing can actually irritate the skin further.
- “It’s a rash or fungal infection” — antifungal creams won’t touch it.
- “It’s just hyperpigmentation” — while there is a melanin component, the cause is metabolic, not sun exposure.
If you’ve ever been made to feel embarrassed about these patches, please know: they are a metabolic skin signal, not a hygiene issue. You are not alone in having been misunderstood about this.
Understanding the full picture of PCOS skin changes — including how hormonal acne in PCOS differs from ordinary breakouts — can help you build a clearer conversation with your healthcare provider.
What Actually Helps
The most important thing to understand is that treating the skin alone is a temporary fix. Addressing the underlying insulin resistance is what makes a lasting difference.
Lifestyle approaches
- Low-glycaemic eating: Reducing refined carbohydrates and sugar helps keep insulin levels steadier. This doesn’t mean a crash diet — it means choosing whole grains, vegetables, legumes, and protein over white bread and sugary drinks. A registered dietitian familiar with PCOS can personalise this.
- Regular movement: Even moderate physical activity — walking, swimming, cycling — improves insulin sensitivity over time. You don’t need an intense regime.
- Sleep and stress: Both poor sleep and chronic stress worsen insulin resistance. Managing these is genuinely part of the treatment picture.
Medical options
- Metformin: A medication commonly prescribed in PCOS to improve insulin sensitivity. The Menopause Society and NICE guidelines recognise it as a standard option for PCOS-related insulin resistance. A GP or endocrinologist decides whether it’s appropriate for you — dosing is always individualised.
- Topical treatments: Dermatologists sometimes use prescription creams (such as retinoids or keratolytics) to improve the skin’s appearance, but these address the symptom not the cause.
- Treating PCOS holistically: Managing androgen levels through hormonal treatments (such as the combined contraceptive pill, where appropriate) can have downstream benefits for skin, though this is very much an individual conversation with your doctor.
Understanding how insulin resistance connects to other PCOS symptoms can help you see why a joined-up approach tends to work better than treating each symptom in isolation.
It’s also worth exploring how PCOS is diagnosed and what tests to ask for, especially if you’ve had patches for a while but never had a formal insulin or glucose assessment.
When to See a Doctor
You should speak to your GP or a PCOS specialist if:
- You have dark velvety patches and haven’t been assessed for insulin resistance or PCOS.
- The patches are spreading rapidly or appearing in unusual places — in rare cases, acanthosis nigricans can be associated with other conditions that need ruling out.
- You have PCOS and have never had fasting glucose or insulin checked.
- The skin is itchy, sore, or inflamed — this needs investigation as it may be something else.
- You feel distressed about your skin and it’s affecting your quality of life — that is a completely valid reason to seek support.
A good clinician will not dismiss these patches. If yours does, it is entirely reasonable to ask: “Could this be linked to insulin resistance?” and to request a blood test.
Frequently Asked Questions
Can acanthosis nigricans go away with PCOS treatment?
Yes, it can improve — sometimes significantly — when the underlying insulin resistance is addressed. Women who improve their insulin sensitivity through lifestyle changes or medication often report the patches fading over months. It may not disappear completely, but it frequently becomes much less noticeable.
Is acanthosis nigricans a sign of diabetes?
It’s a sign of insulin resistance, which does raise the risk of developing Type 2 diabetes over time. Having acanthosis nigricans with PCOS doesn’t mean you have diabetes, but it is a reason to have your blood glucose checked and monitored regularly by your GP.
Will scrubbing or skin-lightening creams help?
Scrubbing won’t remove it and can irritate the skin. Over-the-counter skin-lightening creams are unlikely to make a meaningful difference. The most effective approach is treating the insulin resistance that’s causing the patches. A dermatologist can advise on any prescription topical options if appearance is a concern.
Does everyone with PCOS get acanthosis nigricans?
No. Not all women with PCOS develop these patches — it depends on the degree of insulin resistance present and individual skin factors. Its absence doesn’t mean insulin resistance isn’t there; its presence is simply a useful visible indicator worth investigating.
Where does acanthosis nigricans most commonly appear in PCOS?
The back of the neck is the most common site, followed by the armpits and groin. Women sometimes notice it first as a “dirty” line at the collar — it has nothing to do with cleanliness and everything to do with how high insulin levels affect skin cells in skin folds.
This article is for general information and is not medical advice. It was reviewed by a certified healthcare professional in line with our editorial policy, and we update our content as the science evolves — but every woman’s body is different, so please speak to a qualified healthcare professional about your own symptoms.