Dark Knuckles: Causes, Treatment, And Prevention

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Medical News TodaySubscribeCauses and treatment of dark knuckles

Medically reviewed by Debra Sullivan, Ph.D., MSN, R.N., CNE, COI — Written by Jesse Klein — Updated on November 29, 2023

Causes
Treatment
Home remedies
Prevention
When to see a doctor
Summary

Dark knuckles can indicate a metabolic condition, medication side effect, or other condition. Dark patches of skin can occur due to hyperpigmentation, which happens when the skin produces more melanin, the pigment that gives skin its color, than usual.

Dark patches of skin on the knuckles are common among people with darker skin tones. However, anyone can develop dark knuckles. This symptom is usually harmless, but it can sometimes indicate an underlying health condition.

Sometimes, dark knuckles do not have an obvious cause.

In this article, we discuss some of the possible causes of dark knuckles, as well as treatments, home remedies, and when to see a doctor.

Causes of dark knuckles

close up of a hand with dark knuckles — Dark knuckles do not always have an obvious cause.

Acanthosis nigricans

Acanthosis nigricans (AN) is a skin condition that causes small patches of skin, often near the knuckles, to darken, thicken, and become velvety to the touch. AN often takes months or years to appear, and it can cause the skin to have a bad odor or itch.

Other areas where AN develops include:

armpits
neck
groin area
elbows
knees
bellybutton
beneath the breasts
face
female genitalia

Some people are more likely than others to get AN. These individuals include people who:

have overweight or obesity
are of Native American, African, Caribbean, or Hispanic descent
have a family history of AN

AN is not contagious or harmful on its own, but it can be a precursor to other medical issues, such as:

Prediabetes or diabetes

Darkening skin can signify that a person is starting to develop diabetes. Many of those most at risk for AN are also at higher risk for diabetes.

Prediabetes means that a person’s blood sugar levels are higher than normal. If a doctor is able to identify prediabetes early, a person may be able to prevent full diabetes from developing by making lifestyle changes.

Hormonal conditions

AN can also signal a thyroid or adrenal condition or a hormonal imbalance, such as polycystic ovary syndrome (PCOS). PCOS causes females to produce too much testosterone, leading to fertility issues, pelvic pain, acne, weight gain, and menstrual irregularities.

Cancer

If AN develops suddenly, it may be a sign of cancer, particularly cancer of the stomach, liver, or colon.

Dermatomyositis

Dermatomyositis is a rare disease that causes muscle weakness through chronic muscle inflammation. One of the first and most recognizable symptoms is a patchy bluish-purple or red rash in areas of skin covering the muscles near the joints. These include the muscles near the knuckles, elbows, heels, and toes.

Other symptoms include:

muscle weakness and pain
deposits of calcium under the skin, called calcinosis
hard, painful nodules
unexplained weight loss
fever
inflamed lungs

Dermatomyositis is not curable, but early detection can help relieve the symptoms and slow down its progression.

Addison’s disease

Addison’s disease is an autoimmune condition in which the body mistakenly attacks the adrenal glands, resulting in low levels of cortisol and aldosterone.

An initial symptom of Addison’s disease is areas of darker skin near scars and skin creases, such as the knuckles. This discoloration provides an early clue, as it can develop months or years before any other symptoms.

Other symptoms of Addison’s disease include:

fatigue
vomiting and, sometimes, diarrhea
nausea
abdominal pain
mood changes
irregular menstrual periods

A person can manage Addison’s disease with hormone replacement therapy to replenish cortisol and aldosterone in the body.

Vitamin B-12 deficiency

Dietary factors can also cause dark knuckles. A 2016 study showed that knuckle pigmentation is an external sign of a vitamin B-12 deficiency. Other symptoms of a vitamin B-12 deficiency include:

fatigue
weakness
constipation
loss of appetite
weight loss
numbness and tingling in the hands and feet

A person with a diagnosed vitamin B-12 deficiency can adjust their diet to include more foods that are high in vitamin B-12, including:

fish
meat
poultry
eggs
milk

Vegetarians and vegans will likely need to add vitamin B-12 supplements or fortified foods to their diet to meet their daily requirements.

Raynaud’s disease

The main symptom of Raynaud’s disease is blood vessels in the fingers or toes narrowing in response to stress or the cold. This phenomenon can trap blood in the fingers, causing blue discoloration.

Raynaud’s disease sometimes occurs on its own, but it can also be a secondary symptom of another health condition, such as scleroderma or arthritis.

Drug reaction

One case study found that specific drugs are more likely than others to cause hyperpigmentation. These include:

nonsteroidal anti-inflammatory drugs (NSAIDs)
antibiotics, such as tetracyclines
anticoagulants
antiretrovirals
heavy metals

Medication is more likely to cause hyperpigmentation if a person takes more than one type of drug.

Treatment

Once a doctor identifies the underlying cause of dark knuckles and prescribes treatment, the discoloration should improve. If a medication is causing the hyperpigmentation, a doctor can offer an alternative drug or dosage.

If there is no underlying cause, or a doctor decides not to treat the hyperpigmentation, home remedies can help lighten dark knuckles.

Home remedies for dark knuckles

Although dark knuckles themselves do not medically require treatment, people who wish to try at-home treatments to lighten dark knuckles can try the following:

Turmeric

Curcumin is an active compound in turmeric. A 2012 study found that curcumin interrupts the tyrosinase enzyme. This specific enzyme synthesizes melanin, so inhibiting it may help minimize skin darkening.

To use turmeric, a person can combine a small amount of water with this spice and apply the paste to their knuckles for a few minutes.

Tea

A person can also use tea to lighten darker areas of skin. A 2015 study showed that one of the compounds in black, white, and green tea — epigallocatechin gallate — also inhibits tyrosinase and so can help lighten dark knuckles.

A person should steep a tea bag in hot water, let it cool, and then soak a cotton ball in the tea. They can apply the liquid to the knuckles a few times a day.

Vitamin C

Vitamin C is an antioxidant that can help with a variety of skin concerns, including hyperpigmentation. Many skin care products on the market contain vitamin C.

Research suggests that the most effective vitamin C products have a concentration of 10–20%. Higher strengths do not increase the vitamin’s biological significance and may cause irritation.

Alternatively, if a person would rather use an over-the-counter skin product, the American Academy of Dermatology recommend looking for formulas that contain:

azelaic acid
glycolic acid
kojic acid
retinoids (retinol, tretinoin, adapalene gel, or tazarotene)

Prevention

It is not possible to prevent many of the underlying conditions that cause dark knuckles. However, a person can help prevent hyperpigmentation by using sunscreen before going outside.

Avoiding medications that cause hyperpigmentation may also help, but a person should speak to their doctor before stopping a medication.

When to see a doctor

As darkening knuckles can indicate an underlying health condition, it is important to see a doctor about sudden changes to this area of the skin. If a person has noticed other symptoms, a doctor will be able to find the cause.

Summary

Dark knuckles are not usually a cause for concern and do not themselves require treatment. Sometimes, though, they are a sign of an underlying condition. Once a doctor has determined whether a disease is causing the skin to darken, a person can take steps to address it.

Treating the underlying disease should improve the hyperpigmentation. However, if it persists, or there is no underlying condition to treat, a range of home remedies and products can help people manage dark knuckles.

Dermatology
Nutrition / Diet

How we reviewed this article:

SourcesMedical News Today has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Acanthosis nigricans: Overview. (n.d.). https://www.aad.org/public/diseases/a-z/acanthosis-nigricans-overview
Addison's disease. (2018). https://rarediseases.org/rare-diseases/addisons-disease/
Alexis, A. F., & Blackcloud, P. (2013). Natural ingredients for darker skin types: Growing options for hyperpigmentation [Abstract]. https://www.ncbi.nlm.nih.gov/pubmed/24002160
Al-Niaimi, F., & Chiang, N. Y. Z. (2017). Topical vitamin C and the skin: Mechanisms of action and clinical applications. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5605218/
Dermatomyositis. (2020). https://rarediseases.info.nih.gov/diseases/6263/dermatomyositis
Desai, S. R. (2014). Hyperpigmentation therapy: A review. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4142815/
Giménez García, R. M., & Molina, S. C. (2019). Drug-induced hyperpigmentation: Review and case series. https://www.jabfm.org/content/jabfp/32/4/628.full.pdf
Hassan, S., & Zhou, X. (2019). Drug induced pigmentation. https://www.ncbi.nlm.nih.gov/books/NBK542253/
How to fade dark spots in skin of color. (n.d.). https://www.aad.org/public/everyday-care/skin-care-secrets/routine/fade-dark-spots
Kim, Y. C., et al. (2015). Anti-melanogenic effects of black, green, and white tea extracts on immortalized melanocytes. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4483495/
Lakshman, A., et al. (2016). Knuckle pigmentation: A clue to systemic illness. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5074973/
Raynaud's. (n.d.). https://www.nhlbi.nih.gov/health-topics/raynauds
Tu, C. X., et al. (2012). Curcumin inhibits melanogenesis in human melanocytes [Abstract]. https://www.ncbi.nlm.nih.gov/pubmed/21584871
Vitamin B12: Fact sheet for consumers. (2016).https://ods.od.nih.gov/pdf/factsheets/Vitaminb12-Consumer.pdf
Vitamin C: Fact Sheet for Health Professionals. (2020). https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/
What are the symptoms of PCOS? (2017).https://www.nichd.nih.gov/health/topics/pcos/conditioninfo/symptoms

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Medically reviewed by Debra Sullivan, Ph.D., MSN, R.N., CNE, COI — Written by Jesse Klein — Updated on November 29, 2023

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