Acanthosis nigricans is a darkened, velvety-feeling patch of skin, most often on the neck, in the armpits and in the groin folds. It is not a cosmetic defect but a common skin sign of insulin resistance and excess insulin.
The American Diabetes Association lists acanthosis nigricans among the signs that indicate a risk of diabetes.
Why it appears
With insulin resistance the body produces a lot of insulin. The excess insulin stimulates the growth of skin cells (keratinocytes and melanocytes), which makes the patches thicken and darken.
What it warns about
Acanthosis nigricans is associated with obesity, metabolic syndrome, polycystic ovary syndrome and an increased risk of type 2 diabetes. Less often it is linked to certain medications; very rarely it can be a sign of a tumor.
What to do
The main thing is not to bleach the skin but to address the cause: losing weight and reducing insulin resistance reduce the changes. It is worth checking blood sugar, HbA1c and seeing a doctor.
Calculate using this marker
Calculators where Acanthosis nigricans is used directly:
Frequently asked questions
Can acanthosis nigricans be treated?
On its own it reflects your metabolism, so what gets "treated" is the cause: reducing weight and insulin resistance. As that happens, the skin usually lightens gradually. Topical products give only a cosmetic effect without addressing the cause.
Does it always mean diabetes?
No. More often it is a sign of insulin resistance and an increased risk of diabetes, not diabetes itself. But it is a strong reason to check blood sugar and HbA1c and to assess your metabolic health.
Related terms
Sources
- González-Saldivar G et al. Skin manifestations of insulin resistance: acanthosis nigricans and acrochordons. Postgrad Med J, 2020
- MedlinePlus (NIH) — Acanthosis nigricans