Acanthosis nigricans

Acanthosis nigricans is the name for dry, dark patches of skin that usually appear in the armpits, neck or groin. It could be a sign of an underlying condition, so it needs to be checked by a GP.

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.

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.

• 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

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.