Black Toenail: 6 Potential Causes - Medical News Today

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6 potential causes of a black toenail

Medically reviewed by Debra Sullivan, Ph.D., MSN, R.N., CNE, COI — Written by Jenna Fletcher — Updated on June 19, 2024

Overview
Trauma
Injury
Infection
Melanoma
Pigmentation changes
Other conditions
Treatment
Prevention
Contacting a doctor
Outlook
Summary

Black toenails can result from an injury, a fungal infection, or pigmentation changes over time. More serious causes include heart disease or melanoma.

Treatment for black toenails will vary depending on the cause.

This article looks at six potential causes of a black toenail, treatment options, and tips for prevention.

Causes of a black toenail

A pair of feet on a shadowed sofa, representing a black toenail. -3 — Maite Pons/Stocksy United

The cause of a black toenail may be benign or quite serious.

It is important for a person who develops a black toenail to understand some of the potential causes.

When in doubt, it may be helpful to contact a medical professional who can diagnose the problem and develop an effective treatment plan.

1. Repetitive trauma

When a person wears shoes that do not fit correctly, they may be at risk of developing black toenails due to repetitive trauma.

Long-term pressure on the toes from shoes that do not fit correctly can damage the toenails, especially the big toe.

For example, tight shoes can cause a toenail to get pinched and jammed, causing bleeding underneath the nail and resulting in a black color.

In mild cases, the black toenail will grow out naturally over time without treatment. In severe cases, such as when the nail begins to detach from the nail bed, a person should seek medical treatment.

2. Blunt force

In some cases, the trauma may be a one-time blunt-force injury, for example, if a person drops a heavy object on their foot or toes. When this happens, blood vessels in the nail bed break, causing blood to pool.

The injured toe will start to hurt, and blood will pool beneath the skin almost immediately. The buildup of blood will cause the toe to feel painful and swollen.

A doctor can treat this condition by draining the blood with a needle.

3. Fungal infections

Fungal infections, such as foot fungi or athlete’s foot, can also cause black toenails.

Typically, a fungal infection causes white or yellowish discoloration. However, debris can build up near the infection, causing the nail to appear black.

Toenails are particularly susceptible to fungal infections, as socks and shoes can provide a warm and moist breeding ground for a fungus to grow.

4. Melanoma

In rare cases, a black toenail may be due to melanoma, the most aggressive form of skin cancer.

Melanoma causes the skin to develop one or more patches of dark, irregular-looking skin. In some cases, the patch of darkening skin grows beneath the nail bed.

Melanoma develops slowly and without other symptoms, so people often do not notice it in the early stages, especially if it originates under the toenail.

5. Pigmentation changes

A person’s skin tone can change over time, and pigmentation changes can also affect the skin under the toenails.

For people with darker skin, a dark patch may develop beneath the toenails. Fingernails may also develop darker patches on the nail bed.

6. Underlying conditions

Several medical conditions may cause black toenails, including:

diabetes
kidney disease
heart disease
anemia

In most cases, managing the underlying condition will help the nail to regain its original color.

Treatment for a black toenail

Treatment for black toenails will vary depending on the cause.

In cases of blunt force injury, a doctor may use a needle to make a small hole in the nail. This will allow the blood to drain and alleviate some of the pressure that has built up over time.

In more severe cases where an infection has developed, a doctor may need to prescribe additional medication to help the injury heal.

If a person has a repetitive injury, such as from shoes that do not fit correctly, a doctor will likely recommend resting the foot and wearing different shoes.

If there are underlying conditions such as diabetes, a doctor will first need to treat the condition. They may also adjust the person’s regular treatment regime.

A person may be able to treat a fungal infection at home. Creams and ointments available over the counter and online may be enough to clear the fungus and allow the nail to heal.

However, if the infection does not go away after a few days, a person should consult a doctor.

If a black toenail is cancerous, a doctor will review the available treatment options.

Preventing black toenails

Preventing black toenails from forming is not always possible. However, a person can take steps to reduce their risk of developing black toenails, including:

wearing shoes that fit correctly
having the correct footwear, for example, for the gym or for work that requires protecting the feet
wearing the relevant footwear when using a public shower
treating underlying medical conditions

When to contact a doctor about a black toenail

It is best to contact a doctor if a person experiences a sudden, unexplainable black toenail or if it does not heal with time and at-home treatments.

In cases of trauma or injury, the discolored part of the nail will disappear as the nail grows out.

People can usually treat fungal infections at home, and they may not require a doctor’s diagnosis.

Outlook for a black toenail

Black toenails do not typically cause further problems when they result from trauma or pigmentation changes.

When treated correctly, fungal infections usually cause no further problems. However, fungal infections may spread to other parts of the foot and body if left untreated.

If a person is diagnosed with melanoma, they may receive cancer treatment, depending on the stage and severity of the disease.

In most cases, black toenails require minimal treatment and do not cause additional problems.

Summary

A black toenail is usually not cause for concern and, in many cases, will clear up by itself over time.

It usually results from injury or a fungal infection. In rare cases, however, a black toenail can be a sign of melanoma.

It is advisable to contact a doctor if a person experiences a sudden, unexplainable black toenail or if it does not heal with time and treatment at home.

Dermatology
Diabetes
Infectious Diseases / Bacteria / Viruses
Melanoma / Skin Cancer

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.

Black toenails. (n.d.).https://www.foothealthfacts.org/conditions/black-toenails
Five tips for healthy feet. (2019).https://www.aofas.org/news/press-releases/2019/04/16/five-tips-for-healthy-feet
Melanoma facts and stats. (n.d.).https://www.melanoma.org/understand-melanoma/what-melanoma/melanoma-facts-and-stats
Nail care secrets. (n.d.).https://www.aad.org/media/stats/prevention-and-care/nail-care

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Medically reviewed by Debra Sullivan, Ph.D., MSN, R.N., CNE, COI — Written by Jenna Fletcher — Updated on June 19, 2024

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