Changes in skin colour can be a sign there is internal disharmony, according to Fiona Tuck.

103047049Dirty looking marks on the skin is a condition called Acanthosis Nigricans, AN for short. Fortunately this is uncommon; however, the pseudo form of acanthosis nigricans, isn’t. Faux Acanthosis Nigricans looks identical to its more serious counterpart.

What is Acanthosis Nigricans?

Since ‘Acanthosis’ means thickening or overgrowth of the upper layers of the skin, and ‘Nicgricans’ means dark or black – put it together and we really do get a description where you expect to see – a dark thickening or overgrowth of skin. AN is a brown to black, poorly defined, velvety hyperpigmentation of the skin. It is usually found in body folds, such as the folds in the back of the neck and lateral folds of the neck, under the armpits, groin, thighs and naval, as these are the areas of the body where the skin tends to rub together.

Hormone Insulin

AN can be caused by higher than normal levels of the hormone insulin, due to an insulin resistance in the body. The hormone insulin is responsible for getting your blood sugar into your cells for energy. If your insulin isn’t working well, the pancreas will produce more and more insulin to try and get blood sugars into the cells. The skin cells react by changing the level of colour or pigment in the skin but this only occurs in skin that has already been stretched or rubbed.


AN can also stem from medications (such as the contraceptive pill or corticosteroids) or certain endocrine diseases such as polycystic ovaries, diabetes (the next step to having high insulin levels), hypothyroidism, and other less common hormonal imbalances. AN can also be a sign of an internal cancer related back to gastro, intestinal tract, the ovaries or even the lung, prostate or breast. There are still some cases of AN who have no apparent association to disease, and they are not


AN is diagnosed by detecting the characteristic skin changes during skin examinations. Sometimes a skin biopsy is obtained for lab examination. If the cause of AN is unclear, other investigations may be required such as blood test, X-ray and other test to identify the underlying cause.

Weight-related AN

For the first group who have AN as a result of being overweight or certain endocrine diseases – treating the underlying condition will result in a remarkable improvement in the Acanthosis. A change in diet can be beneficial in reversing insulin resistance, and inflammation. Regular exercise and a low GI, high fibre, wholefood diet will support health, wellbeing and reduce blood glucose levels thereby dramatically reducing the risk of associated diseases such as Metabolic Syndrome and Type 2 diabetes.

In most cases AN is not harmful and it is definitely not contagious – but medical attention is required to ensure there is no other underlying disease that may require medical treatment.

Fiona Tuck is managing director of Skinstitut, visit