Check if you have acanthosis nigricans
The main symptom of acanthosis nigricans is patches of skin that are darker and thicker than usual.
They can appear anywhere on the body.
They're most common in skin folds, such as the armpits, neck or groin
Some people also have tiny growths on the patches
The patches often appear gradually without any other symptoms.
Sometimes the skin may be itchy.
When to get medical help
See a GP if you have:
- new dark patches on your skin
- any skin changes you're unsure about
Although it's usually harmless, it's best to get any skin changes checked out.
In rare cases, it can be a sign of something more serious, such as cancer.
A GP can usually tell if it's acanthosis nigricans by looking at your skin.
You may need some tests if they're not sure what's causing the patches.
Causes of acanthosis nigricans
The most common cause of acanthosis nigricans is being very overweight.
Other causes include:
- type 2 diabetes
- conditions that affect hormone levels – such as Cushing's syndrome, polycystic ovary syndrome or an underactive thyroid
- taking certain medicines – including steroids or hormone treatments like the contraceptive pill
- in rare cases, cancer – usually stomach cancer
- in rare cases, a faulty gene inherited from your parents
Sometimes acanthosis nigricans happens in healthy people with no other conditions. This is more common in people with dark skin.
Treating acanthosis nigricans
Once your GP knows what's causing the condition, they can recommend the best treatment.
The patches should fade over time once the cause is treated.
If you're very overweight, your GP may recommend losing weight.
Depending on the cause, they may also recommend:
- medicine to balance your hormones
- medicine to balance your insulin levels
- changing your medicine to one that doesn't cause the patches
There's no specific treatment for the patches. A skin specialist (dermatologist) may be able to suggest treatments to improve their appearance, but finding and treating the cause is usually recommended first.