These are the first symptoms.

**What Skin Changes Mean**

Dark, velvety patches on the neck, armpits, or groin may look like dirt, but they can indicate acanthosis nigricans, a skin condition often linked to insulin resistance and high blood sugar levels.

These patches cannot be removed by rubbing and are not caused by poor hygiene.

**Causes and Risk Factors**

Acanthosis nigricans is not a disease itself, but rather a warning sign.

Common causes include insulin resistance, obesity, hormonal disorders, genetic factors, and, rarely, medications or tumors.

Children and adults with obesity who develop these patches may have an increased risk of developing type 2 diabetes.
**Diagnosis and When to See a Doctor**