Dark Armpit Skin: What Causes It?

What causes dark armpit skin? If your armpits have noticeably changed in colour, it could be Acanthosis Nigricans, a medical condition and potentially a symptom of underlying health conditions.

A rise in awareness about potentially harmful ingredients absorbing into the bloodstream and lymph system via the armpits has led to more people seeking natural deodorant alternatives than ever before.

In very rare cases, the transition from synthetic aluminium antiperspirant to a natural alternative doesn’t quite go as planned.

(Read this to make your transition easier)

When this happens, the most common reaction is to assume the new deodorant is at fault. It’s likely the only product being applied to the underarms other than soap so, on the surface of things, that makes sense.

However, a sudden change in the colour of your underarm skin should not be attributed to using natural deodorant alone.

Learn How To Reduce Your Exposure To Harsh Chemicals

According to the The National Center for Biotechnology Information, armpit discolouration (dark and even bruised-looking underarm skin) could be a symptom of Acanthosis Nigricans, which is a medical condition and may be a red flag for severe underlying health problems. (1)

What is Acanthosis Nigricans?

Dark, thick, sometimes purple-ish skin that appears most commonly under the arms, neck or groin.

Acanthosis nigricans is characterized by dark, coarse and thickened skin with a velvety texture, being symmetrically distributed on the neck, the axillae (armpits), and groin folds, histopathologically characterized by papillomatosis and hyperkeratosis of the skin.” (2)

Acanthosis Nigricans on Light Skin Tone

Acanthosis Nigricans on Dark Skin Tone

Who gets Acanthosis Nigricans?

Prevalence varies according to age, race and degree of obesity, appearing most commonly in people with dark skin tones. Due to the rising rates of obesity and diabetes in western society, a higher prevalence of Acanthosis Nigricans has been observed recently. (3)

Does natural deodorant cause dark armpit skin?

The tendency of Acanthosis Nigricans to appear on the neck, groin and armpit areas suggests that perspiration or friction may be cofactors but are not the root cause. This may explain why Acanthosis Nigricans might seem to appear when you switch from an antiperspirant (blocks sweat) to natural deodorant, which does not typically stop sweat. (4)

What causes Acanthosis Nigricans (dark armpit skin)?

According to a 2018 study by the British Journal of Medicine, there are a variety of factors that can trigger Acanthosis Nigricans, including medications; birth control pills, thyroid medication, growth hormones, some body building supplements, and even some medications used to ease the effect of chemotherapy, and genetics. In rare cases Acanthosis Nigricans is the symptom of more serious underlying health problems, such as Type 2 Diabetes, gastric cancer, Addison’s disease, hypothyroidism, Cushing’s disease and polycystic ovarian disease. (5)

Dark armpit skin might be a sign of Diabetes

Acanthosis Nigricans is very closely associated with insulin resistance.

Insulin resistance is a metabolic disorder in which target cells fail to respond to normal levels of circulating insulin. This results in hyperinsulinemia, which may represent an easily identifiable sign of Type 2 Diabetes. (6)

What Causes Dark Armpit Skin?

At high concentrations, insulin exerts potent growth-promoting effects and stimulates keratinocytes and fibroblasts, leading to Acanthosis Nigricans. (7)

What to do if your armpit skin colour darkens or changes

Acanthosis Nigricans can be induced by medication, genetics or hormones but it can also be a pointer to serious underlying health problems. An appointment with your primary healthcare provider should be made as a priority to help prevent any long term consequences.

Full Scientific Studies

READ THE FULL NCBI STUDY

READ THE FULL BRITISH JOURNAL OF MEDICINE STUDY

References

(1), (2), (3), (4), (6), (7): An Approach To Acanthosis Nigricans

Indian Dermatol Online J. 2014 Jul-Sep; 5(3): 239–249.

doi: 10.4103/2229-5178.137765

Meghana Madhukar Phiske

(5), Acanthosis Nigricans in Pre-diabetic States

British Journal of Medicine 2018;11(1):a1105 James Paul Pandarakalam

As always, we are here to provide information and resources. The content in this post is not intended as medical advice. Please read our General Health & Wellbeing Disclaimer for details.

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