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Acanthosis nigricans, armpits and darkened skinfolds?


Acanthosis nigricans, armpits and darkened skinfolds?  


Acanthosis nigricans is characterized by thickening, hyperpigmentation of the skin, which appears gradually and gradually. The area most affected is the posterior region of the neck, followed by the armpits, lateral side of the neck, flexor surfaces of the limbs, periumbilical region, inframammary, oral mucosa, soles of the feet and palm of the hands. Its physiopathology is related to the excessive stimulation of keratinocytes and cutaneous fibroblasts through the activation of receptors of insulin growth factors in these cells. The most effective treatment involves treating the cause of Acanthosis nigricans. However, while this is unknown, topical products derived from these retinoids are used, in addition to oral medications, and dermabrasion or laser therapy.


What is Acanthosis nigricans? 

Acanthosis nigricans is a very common skin pigmentation disorder characterized by hyperkeratosis (excess of keratin) and hyperpigmentation (gray and thickened lesions that give a warty appearance). Dark spots on the skin with a thick, velvety texture are the most common signs of Acanthosis nigricans. The affected areas of the skin cause pruritus (itching) or may have a specific odor. Acanthosis nigricans can be a sign of a more serious health problem such as pre-diabetes (read more on pre-diabetes below). These skin blemishes tend to disappear after successfully treating the root condition of the problem. It is also associated with obesity and endocrinopathies, such as hypothyroidism or hyperthyroidism, acromegaly, polycystic ovarian disease, metabolic syndrome, and Cushing's Syndrome.


Where can Acanthosis nigricans appear in the body?

The most common sites for the appearance of these spots are the skin folds. You may see:   -> neck (back)


--> in the armpits


--> in the elbows


--> on your knees


--> on your lips


--> in the periumbilical region


--> in the inframammary region 

--> in the oral mucosa


--> in the groin


--> in the palm of the hands (rarer)


--> on the sole of the feet (rarer)


What types of Acanthosis nigricans are there?

  1. Miescher Syndrome: benign and hereditary form
  2. Gougerot Carteaud Syndrome: Benign and possibly hereditary, but appears in young women.
  3. Pseudo-Acanthosis nigricans: a benign juvenile form that is associated with obesity and endocrinological changes.
  4. Malignant acanthosis: Adult paraneoplastic manifestation that is often associated with tumors of the digestive tract and liver, as well as lymphomas and melanoma.

What are the causes Acanthosis nigricans?

The armpits and the rest of the skin on your body should naturally have the same tone. However, underarm or other skin may darken. Skin color is determined by cells called melanocytes, which give skin pigmentation. When melanocytes multiply more than usual, they give a darker tone to the skin. Underarm darkening is often not a sign of anything serious, but it can become an embarrassing situation, especially during warmer seasons, when we are wearing less clothes and having our armpits exposed.

Anyone can develop Acanthosis nigricans, but people with darker skin are more prone to darkening under their arms than people with lighter skin. Hair removal can also be a cause. Irritation caused by repeated shaving or shaving stimulates excessive melanocyte production. To avoid irritating your armpits, lubricate your skin with mild soap or shaving cream before shaving. Apply an unscented moisturizer later.

Excess Insulin

The most common trigger for Acanthosis nigricans is excess insulin in the bloodstream.

When is there too much insulin in the blood?

When a food is eaten, the body converts carbohydrates into sugar molecules, such as glucose. Part of this glucose is degraded in cells to obtain energy. Another part is stored. Insulin is the hormone that drives glucose into cells so that these metabolic reactions occur.

Overweight people tend to develop insulin resistance over time. Although the pancreas continues to produce insulin, the body cannot use it properly. In this way, glucose accumulates in the bloodstream. Glucose builds up, causing high levels of glucose and insulin in the blood.

Excess insulin causes normal skin cells to reproduce rapidly. For those with dark skin, these new cells have more melanin. This increase in melanin gives the skin a darker patch than its surroundings. Thus, the presence of Acanthosis nigricans is a strong predictor of future diabetes.

If excess insulin is indeed the cause, it is relatively easy to correct with proper diet, exercise and blood sugar control.


Excess insulin in the blood of an obese individual is the most common cause of Acanthosis nigricans dysfunction.

Obese or overweight people carry extra weight which leads to insulin resistance and therefore the body does not use this hormone properly. Insulin builds up in the body and causes skin pigment cells to multiply very quickly, causing the epidermis - the outermost layer of the skin to darken.

Type 2 diabetes

Obesity is a risk factor for type 2 diabetes, a disease where blood sugar parameters are high. People who develop type 2 diabetes are at greater risk for Acanthosis nigricans.

Hereditary Genes

The condition is transmitted in an autosomal dominant manner, meaning that even if only one of the patient's parents has the affected gene, the offspring will develop this skin dysfunction. Despite this finding, Acanthosis nigricans is rarely of hereditary origin.

Use of Certain Medicines and Supplements

Continued use of medications such as birth control pills, growth hormones, high dose niacin, thyroid controlling drugs, corticosteroids such as prednisone, bodybuilding supplements can cause dark spots on certain areas of the body. All of these medicines can cause changes in insulin levels. Drugs used to alleviate the side effects of chemotherapy were also associated with Acanthosis nigricans. In most cases, the condition disappears when medications are discontinued.

Hormonal changes

Acanthosis nigricans may be related to hormonal syndromes and / or disorders, which disturb insulin levels, including:

  • Polycystic ovary syndrome: deregulates ovarian functioning which contributes to irregular menstrual periods, infertility, acne and weight gain;
  • Cushing's Syndrome: The high level of cortisol in the body causes stretch marks, weight gain and black ;
  • Acromegaly: a condition that causes a significant increase in growth hormone secretion, causing an overgrowth of various body tissues;
  • Hypothyroidism: caused by dysfunction of the thyroid gland, which does not produce enough hormone, contributing to weight gain and tiredness.


If the dark spots characteristic of Acanthosis nigricans appear too quickly, it may be a sign of cancer, particularly that of the stomach, liver or colon. These neoplasms increase the levels of growth factors, which in turn stimulate the cells that produce skin pigment. When Acanthosis nigricans is caused by cancer, it is called Acanthosis nigricans malignant. As this is a rare condition, it tends to affect middle aged or elderly people, and the stains are more severe and may also appear on the mouth, tongue and lips.

Who is at risk for Acanthosis nigricans?

Acanthosis nigricans can appear in men and women. There are risk groups that tend to develop Acanthosis nigricans more easily. Are they:

  • Individuals with darker skin.


  • The frequency of Acanthosis nigricans varies among ethnic groups. According to the American Academy of Dermatology, black or African descent, Caribbean or Hispanic people are most at risk.


  • All ethnic groups are equally at risk for Acanthosis nigricans when the body mass index (BMI) is well above normal ie obese or overweight.


  • With family history.
  • Diabetes or pre-diabetic conditions.


Note: Children who develop Acanthosis nigricans are at greater risk of developing type 2 diabetes later in life.

What are the symptoms of Acanthosis nigricans?

The main symptom of Acanthosis nigricans is the appearance of darker-colored spots with a dry and rough texture, sometimes with a velvety texture. These spots often develop slowly. For this reason it is important to be aware of your skin to detect the appearance of something strange. From the spots can develop small warts, called papillomatosis. A histological section with papillomatosis and hyperkeratosis can be seen in the following image.

(Read how to treat papillomatosis at

When to see the doctor?

Dark armpits are usually harmless. But it is worth watching for a dermatologist, especially if you have a condition like diabetes or a thyroid hypoactivity. Treating the condition that caused diabetes or hypothyroidism will make the skin lighten. If you see dark spots on your arms and other areas overnight, see your dermatologist or doctor immediately. This may be a sign of a more serious condition - cancer.

How is the diagnosis made?

Acanthosis nigricans is easy to recognize. The diagnosis can be made through clinical analysis and complementary exams to determine the exact cause of the stains, namely: blood glucose test, insulin test, skin biopsy, endoscopy and x-ray. To help with the diagnosis you should tell the doctor which medicines, dietary supplements, food and vitamins you consume. The cause of Acanthosis nigricans can be more easily diagnosed due to these substances.

What is the treatment for Acanthosis nigricans?

There is no specific way to treat Acanthosis nigricans. Acanthosis nigricans is not a disease, so its treatment varies according to its causes. For example:

  • If obesity is the cause of blemishes, the doctor will probably recommend certain diets so that he can lose weight healthily;
  • Use of medicines that make the hormonal adjustment;
  • Change of medicine that causes symptoms of Acanthosis nigricans;
  • Surgery, chemotherapy or radiotherapy in cases of cancer.
  • The dermatologist may prescribe medications / cosmetics to help alleviate the darkening of the skin. These creams have very specific active ingredients, including:

*Retinoid creams or tablets. Tretinoin (Retin-A) is considered the first line treatment for Acanthosis nigricans. Both retinol and tretinoin are forms of vitamin A. When used regularly, it can help thin and lighten the skin in affected areas. Well-known creams containing vitamin A are Halibut ( and Mitosyl (https: // /




*Chemical peels. Peels containing trichloroacetic acid (TCA) can help exfoliate the skin. This process helps remove thicker and damaged skin to reveal new and smooth skin.

*Calcipotriene (Dovonex). This vitamin D cream reduces skin pigment cells.

*Dermabrasion, which resurfaces the skin, and laser therapies are also used to treat dark skin under the arms.

*Creams with 20% urea in their composition, alpha-hydroxy acids (, salicylic acid, vitamin C (https: // and aloe vera ( de-Aloe-Vera-500ml & search = aloe% 20vera & description = true & page = 2).

*A very effective skin lightening concentrate is Lighting shock and Double vitamin C. You can order both from Mipmed ( The cream with vitamin C is stabilized and can be used in both winter and summer. This means that vitamin C which is photosensitive when stabilized does not stimulate melanin and therefore does not promote darkening of the skin with the sun.

What natural remedies can be applied to whitening Acanthosis nigricans?

These natural treatments can improve the appearance of Acanthosis nigricans, help brighten the color, but do not cure the condition.

Some natural remedies can be used to lighten pigmented skin, namely:

  • sea cucumber extracts
  • curcumin
  • milk thistle extract

These products have not been proven to relieve dark armpits, and some of them can cause side effects. Dialogue with your doctor or dermatologist before using any natural remedy.

NEVER self-medicate or discontinue medication without consulting a doctor. Your doctor will know how to tell you the dosage, duration of treatment and the medicine that is best for you. The information expressed in this article is for informational purposes only, does not supersede expert advice or is intended as a recommendation for any treatment. Always follow package directions and if symptoms persist seek medical advice.

What complications may exist?

Individuals who acquire Acanthosis nigricans are more susceptible to developing type 2 diabetes.

How to prevent?

The use of sunscreen is essential!

In prevention there are behaviors that help prevent Acanthosis nigricans, which are included in a healthy lifestyle. Maintaining healthy habits and a good quality of life not only reduces the risk of contracting Acanthosis nigricans, but also various types of diseases.

Catarina Vilela (Nurse)