Dark skin on your knuckles can have many causes. The darker pigmentation on your knuckles may be inherited. Or it may be a reaction to a drug you’re taking, such as an oral contraceptive, a strong corticosteroid, or niacin.

Darker skin on your knuckles can also be a sign of an underlying condition that needs to be treated, such as diabetes.

Anyone at any age can develop dark knuckles. But they occur more frequently in people with darker skin pigmentation.

Here we’ll look at some possible causes of dark knuckles, as well as various treatments, including home remedies.

Dark knuckles can be a symptom of a variety of health conditions. It can also be caused by a vitamin deficiency and certain drugs. Let’s take a closer look at some of the most common causes.

Acanthosis nigricans

Acanthosis nigricans (AN) is a condition that involves darkening and thickening of the skin in one or more areas on the body, including the knuckles. The darkened skin may feel velvety. It may also feel itchy or have an odor.

AN is fairly common. In a 2010 study, AN was diagnosed in 19.6 percent of the study participants, in all age groups. According to this study, the condition was more prevalent in Native American, African American, and Hispanic populations.

Anyone can get AN, but you’re at more risk if you:

  • are overweight or have obesity
  • have a family history of AN
  • are African American, Native American, or Hispanic
  • are insulin resistant

AN is sometimes inherited and can occur in healthy people. It’s thought to be related to mutations in a gene that involves fibroblast growth factor. But it’s often a symptom or a warning sign of another condition, such as diabetes.

Prediabetes and diabetes

Dark knuckles are most prevalent among people who have diabetes or who have several risk factors for diabetes. Prediabetes means that your blood sugar levels are higher than normal.

According to the Mayo Clinic, prediabetes often has no symptoms, so darkened knuckles can be a warning sign. This is important, because lifestyle changes can help regulate your blood sugar levels and prevent prediabetes from progressing to diabetes.

The relationship of dark knuckles and diabetes isn’t fully understood. It’s thought that high levels of insulin may affect the growth of skin cells.

Vitamin B-12 deficiency

According to a 2016 study, dark knuckles can be an important marker for vitamin B-12 deficiency. Sometimes it may be the only marker for this deficiency. Other symptoms of vitamin B-12 deficiency include:

  • fatigue
  • anemia
  • shortness of breath
  • feeling dizzy or light-headed
  • neurological problems

A 2017 case study reported that about 10 percent of people with vitamin B-12 deficiency have darkened knuckles.

When B-12 deficiency is treated, the skin on the knuckles will likely return to their normal color.

Drug reactions

Some people may develop darkened knuckles because of a drug they’re taking. The most common drugs that can cause this include:

If you’re taking one of these drugs, you may want to discuss alternatives with your doctor. The knuckle darkening usually disappears once you stop taking the drug.

Dermatomyositis

Dermatomyositis is a rare inflammatory disease that can cause muscle weakness and a skin rash. The rash can appear on the knuckles as well as on the face, chest, knees, or elbows.

The rash can be bluish-purple or red in color. Sometimes the rash can appear without any muscle symptoms.

Dermatomyositis most commonly occurs in children between 5 and 15 years old, or adults in their late 40s to early 60s. There’s no cure for this condition, but symptoms can be treated.

Addison’s disease

Addison’s disease is a rare condition. It’s caused by the failure of your adrenal glands to produce enough of the steroid hormones known as cortisol and aldosterone.

Fatigue and darkening in skin color are two common symptoms. The darker skin tends to appear near scars or skin creases like the knuckles. Symptoms can vary, but skin darkening often precedes other symptoms.

About 1 in 100,000 people in the United States has Addison’s disease. It usually affects people between 30 and 50 years old. The condition is treatable with drugs to manage symptoms.

Scleroderma

Scleroderma, also called systemic sclerosis, is a rare autoimmune disease that causes an overproduction of collagen. This leads to the hardening and tightening of the skin and connective tissues. There are many types of scleroderma, and some can be disabling.

One of the symptoms of scleroderma is a reddening of the skin, including your hands and knuckles.

This condition is also linked to Raynaud’s phenomenon, which is often an early symptom of scleroderma. In Raynaud’s, the blood vessels in your fingers and toes contract and may turn blue and painful. This is usually in response to cold temperatures or stress.

Polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) involves the production of higher-than-normal levels of male hormones in women. One of the symptoms may be darkening of the skin, especially in body creases.

PCOS is treatable with drugs and lifestyle changes, such as weight loss and exercise.

Autoimmune disorders

In rare cases, dark knuckles may be associated with an autoimmune disease such as Sjögren’s syndrome or lupus.

If your knuckles become darker and you don’t know why, it’s a good idea to follow up with your doctor. Tell your doctor about any other symptoms you may have, such as fatigue, dizziness, or pain.

It’s especially important to check with your doctor if your knuckles suddenly darken. This may be a sign of a more serious condition that needs immediate treatment.

If your dark knuckles are linked to an underlying health condition, the first line of treatment will involve medication, other types of therapies, or lifestyle changes for that condition.

If underlying conditions are ruled out, there are other options you can try to treat your dark knuckles. These include home remedies, over-the-counter products, and prescription drugs that can treat hyperpigmentation.

Talk with your doctor or dermatologist about the treatments that may work best for you and your skin.

Some common household items that may help lighten your knuckles include:

  • baking soda mixed with water into a paste and applied to your knuckles for 15 to 20 minutes
  • lemon juice applied to your knuckles with a cotton ball daily

It’s a good idea to keep your knuckles and hands moisturized year-round. Also make sure to use sunscreen when you’re outside, even if your skin is naturally dark.

Although moisturizer and sunscreen won’t lighten your knuckles, they can help prevent damage and irritation from the sun, cold weather, chemicals, and hot water.

There are many commercial products that advertise skin “lightening.” Some may be expensive and require long-term use. Be aware that not all commercial products perform as advertised.

Some commonly used OTC skin lightening products contain hydroquinone or lipohydroxy acid, which is derived from salicylic acid.

A dermatological study found that some natural ingredients can help lighten the skin. These natural ingredients, which usually don’t cause irritation, include the following:

  • Soy. It can help lighten the skin and suppress additional pigment from coming to the surface.
  • Niacinamide. This form of vitamin B-3 works in a similar way to soy.
  • Ellagic acid. This acid is derived from strawberries, cherries, and pomegranates. It works to stop an enzyme that’s needed for melanin (skin pigment) production.
  • Lignin peroxidase. This enzyme is extracted from a fungus that’s found in wood pulp. It can break down melanin.

The same study found that the following natural ingredients can also help with skin lightening. However, these ingredients may be more likely to cause an allergic reaction.

  • Arbutin. This is derived from plants, including blueberries and cranberries.
  • Kojic acid. This is derived from a fungus found in wood pulp.
  • Licorice extract. This is available over the counter as Liquirtin.

Aloe leaf extract is another natural ingredient that may help lighten skin, according to a 2012 study.

Be sure to read product labels carefully so you know what types of ingredients are used in a skin lightening treatment.

If other treatments don’t work for you, your doctor may prescribe other topical remedies. Some commonly prescribed drugs for hyperpigmentation include:

Other new prescription products have been developed recently. Two promising drug ingredients for skin lightening are:

  • SMA-432
  • 4-n-butylresorcinol

Talk to your doctor about a treatment plan that works best for you. Also be sure to ask about any side effects from prescriptions or OTC products.

Darker skin on the knuckles is a fairly common issue. It’s often associated with other conditions, most commonly obesity and prediabetes. If your dark knuckles aren’t a symptom of an underlying health condition, the darkened skin is likely not a cause for concern.

If you want to lighten the skin on your knuckles, you can opt for home remedies or store-bought products. If these don’t work, you can ask your doctor about prescription treatments.

It’s a good idea to see your doctor if you notice that your knuckles have darkened. Sometimes it can be a sign of a more serious condition that requires treatment.