A black neck, also called “dark neck,” describes a darker skin tone on the neck than on the surrounding skin. Most of the time, this is harmless and not contagious.

In some cases, however, this skin darkening may be a warning sign of something more serious, so it’s important to see a doctor to determine the cause and begin any necessary treatment. Read on to learn more about black neck, what causes it, and how to treat it.

The primary symptom of black neck is a darkening of the skin on the neck. In some cases, the darkening may also affect other areas of your body, most commonly the armpits.

Other symptoms that may accompany it include:

  • thickened skin
  • skin that feels velvety to the touch
  • itchiness

If the darkening appears suddenly, consult a doctor, as it could be a sign of a more serious underlying condition.

Darkening of the neck may be caused by various conditions including the following:

Acanthosis nigricans

Acanthosis nigricans (AN) is a condition in which the skin turns dark and thick and may feel velvety. It can appear on the neck, in folds of skin, and elsewhere on the body. It’s most commonly found in the armpits, but sometimes in other creases like the groin. It can occur in men, women, and children and may be more common in those with darker skin.

AN isn’t a disease, nor is it contagious or harmful on its own. It’s most often related to one’s insulin level, and is often seen in those with prediabetes or diabetes. Children who develop AN are at a higher risk of developing type 2 diabetes.

Other more serious underlying conditions AN may signal include:

AN may also be caused by various drugs and supplements including niacin, birth control pills, prednisone, and other corticosteroids.

Treatments usually treat the underlying cause of AN. If that isn’t successful then you may be given treatments for the skin like retinoids or vitamin D creams.

Dermatitis neglecta

Dermatitis neglecta is a condition in which one’s skin changes color because it hasn’t been properly washed. It happens after sweat, bacteria, sebum, and other matter builds up due to a lack of hygiene. Also known as “unwashed dermatosis,” it’s a rare disorder but is easily treated by scrubbing the area with soap, water, or alcohol and prevented by maintaining personal hygiene.

Drug-induced skin pigmentation

Hyperpigmentation of the skin may occur as a result of some drugs, including but not limited to:

  • nonsteroidal anti-inflammatory drugs
  • phenytoin
  • antimalarials
  • amiodarone
  • antipsychotic drugs
  • tetracyclines

The discoloration can appear anywhere on the body, including the neck. The colors range from dark brown to blue-black. It typically will resolve once the drug causing it is stopped, however, the discoloration could also be long-term or even permanent. In those cases, laser treatments may be able to remove the hyperpigmentation.

Because black neck isn’t a disease but a symptom of an underlying condition, it’s important to see a doctor if you notice a darkening anywhere on your neck.

AN can typically be diagnosed with a skin check, but your doctor will likely also check you for diabetes and may perform additional tests such as blood tests and X-rays based on your other symptoms.

Treating the underlying condition that’s causing your darkened neck is key to eliminating it and preventing it from recurring. In some cases, the discoloration may resolve when the condition is treated, or in the cases of drug-induced hyperpigmentation, when the medication is stopped. For example, most AN is caused by insulin resistance, which can often be solved with weight loss.

Even if the underlying condition is treated, long-term or permanent discoloration of the skin may remain, which may make you feel self-conscious. There are several options that may help return skin to its original color. While some may be better for certain skin tones, your doctor or a dermatologist can help determine which may be most effective for you.

Treatment options for black neck may include the following:

Dark neck isn’t a harmful or contagious condition on its own. However, it could be the sign of a more serious condition, so you should see your doctor at the first signs of your skin darkening. They can help diagnosis and treat the cause as well as discuss treatment options to help your skin return to its original color.