These Are the First Symptoms of Acanthosis Nigricans
A dark patch of skin can sometimes look like a harmless change in pigmentation. But when the skin becomes darker, thicker, and velvety, especially in certain body folds, it may be a condition called acanthosis nigricans.
It isn’t contagious, and it isn’t simply caused by poor hygiene. In many cases, it can be a visible clue that something else—such as insulin resistance—is affecting the body.
The First Signs to Look For
1. Darkening of the skin
One of the earliest noticeable changes is skin that becomes darker than the surrounding area. It may start subtly and gradually become more obvious.
2. A thicker or velvety texture
The affected skin often doesn’t just change color. It can become thicker and softer or velvety to the touch.
3. Dark patches in skin folds
Common locations include:
- The back and sides of the neck
- Armpits
- Groin
- Inner thighs
- Elbows or knees
- Knuckles
The neck is particularly common, and some people first notice the change while looking in a mirror.
4. Gradual spreading
The patches may slowly become larger or darker over time. They generally aren’t painful.
5. Small skin tags
Some people with acanthosis nigricans also develop small, soft skin tags around affected areas, particularly the neck and armpits.
What Causes It?
Acanthosis nigricans is a skin sign rather than a disease itself.
One common association is insulin resistance. When the body becomes less responsive to insulin, insulin levels may rise, and this can stimulate changes in skin cells.
It can therefore occur in people with conditions such as prediabetes or type 2 diabetes, although having acanthosis nigricans doesn’t automatically mean someone has diabetes.
Other possible associations include obesity, certain hormonal conditions, some medications, and—much more rarely—underlying cancers.
When Should You See a Doctor?
If you develop new, unexplained dark or thickened patches—particularly around your neck or armpits—it’s worth discussing them with a healthcare professional.
A clinician may examine the skin and, depending on your circumstances, consider checking things such as blood glucose or other metabolic markers.
Seek medical evaluation particularly if the changes appear suddenly, spread rapidly, or involve extensive areas of skin.
Can It Go Away?
Treatment depends on the underlying cause.
If insulin resistance, excess weight, a medication, or another medical condition is contributing to the skin changes, addressing that underlying issue may improve the appearance over time.
Skin-lightening products alone generally don’t address the reason acanthosis nigricans developed.
One Important Reminder
Not every dark patch on the skin is acanthosis nigricans. Eczema, fungal infections, post-inflammatory pigmentation, and other skin conditions can look similar.
Don’t diagnose yourself from a photograph alone. A new or changing skin condition should be evaluated if you’re unsure what it is.
If you’d like, you can upload a photo of the skin change and I can explain what features are consistent with acanthosis nigricans and what other possibilities you might discuss with a clinician.