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.
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
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
- rarely, cancer – usually stomach cancer
- rarely, a faulty gene inherited from your parents
Sometimes healthy people with no other conditions get acanthosis nigricans. This is more common in people with black or brown skin.
Once a GP knows what's causing acanthosis nigricans, they can recommend the best treatment.
The patches should fade over time once the cause is treated.
If you're very overweight, a 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 does not cause the patches
There's no specific treatment for the patches themselves. A skin specialist (dermatologist) may be able to suggest treatments to improve their appearance, but finding and treating the cause is usually recommended first.