Black Toenail: Symptoms, Causes, and Treatment (2024)

A black toenail can happen because of an injury that produces a bruise called a subungual hematoma, though it can also have other causes such as a nutritional deficiency or an infection.

Black toenails can be painful, but they often go away on their own. In some cases, they may require treatment from a healthcare provider.

This article will discuss black toenails, including what can cause them, what to do about them, and if you should call your healthcare provider.

What Are the Symptoms of Black Toenails?

The most common symptom of black toenail is exactly that—the nail appears black, which is usually due to blood collecting underneath the nail. However, the discoloration can also be reddish, purplish, or brownish. Other symptoms include:

• Pain
• Nail separates from nail bed over time
• Thickening and splitting of the nail

If the area becomes infected, you may note:

• Swelling
• Odor
• Redness
• Discharge

Some nail discoloration appears as striations, or lines, in the nail that are usually vertical, sometimes called splinter hemorrhage. They are due to bleeding from small capillaries under the nail. Any discolorations that are also painful or don't go away should be assessed by a healthcare provider.

What Causes Black Toenails?

There are several reasons why your toenail can become discolored. The most common include:

• Bruise under the nail due to trauma or pressure
• Fungal nail infection
• Ingrown toenail

Bruise Under the Nail Due to Trauma or Pressure

Trauma resulting in a subungual hematoma is the most common cause of a black toenail. It may be due to stubbing the toe or dropping something on it. The injury bleeds, and the blood is trapped under the nail, where it darkens. The black toenail may fall off a few weeks after it appears and may take up to six months to grow back.

Tight or badly fitting shoes may rub or compress the toes and damage the nail or allow the foot to slide forward with each step and cause repetitive trauma and subungual hematoma.

Fungal Nail Infection

Fungal nail infections are often caused by fungal organisms called dermatophytes. The infection can take hold if there is a cut or crack near the nail, and sweaty feet also contribute to a favorable environment. Diabetes, vascular disease, and a weak immune system make you more vulnerable to toenail fungus.

Ingrown Toenail

With an ingrown toenail, your toenail is growing into the skin surrounding the nail bed. It may lead to bacterial infection, which can discolor the nail.

Underlying Health Condition

Health conditions that affect circulation like diabetes and kidney disease, heart infection, psoriasis, or anemia can cause discolored toenails. In people with diabetes, discolored toenails tend to be more of a yellowish hue, though blackening can occur in some cases.

Melanoma

Rarely, black toenail is due to melanoma. Subungual melanoma is a particular type of skin cancer, and while rare, can be very serious if left untreated.

What Medications Can Cause Black Toenail?

There are medications that can lead to toenail discoloration due to effects on the nail bed, blood supply to the nail, or increased sensitivity to light. These include:

• Cancer drugs: Including tyrosine kinase inhibitors and taxanes
• Antibiotics: Including tetracycline and zidovudine (which is used to treat or prevent human immunodeficiency virus, or HIV)
• Retinoids: Vitamin A derivatives used in skin care
• Psoralens: Light-sensitive drugs used to treat skin conditions like psoriasis
• Plaquenil (hydroxychloroquine): An antimalarial drug also used for some autoimmune conditions

When to See a Healthcare Provider

If you know you injured your toenail, it is not painful, and less than half of the toenail is black, you don't need to go to a healthcare provider. But contact a healthcare provider if any of these apply:

• The toenail hurts.
• The discoloration has appeared slowly.
• More than half of the toenail is black.
• The discoloration has spread outside the nail.
• You also see bumps under the nail.
• You have a health condition such as diabetes or vascular disease.
  

If you have spreading discoloration outside the nail or bumps under the nail, it's important to call a healthcare provider so they can examine you for infection or, in rare cases, skin cancer that needs prompt treatment.

You can also see a dermatologist for a black toenail, especially if you suspect melanoma.

Can a Black Toenail Cause Complications?

Complications from a black toenail can include permanent damage to the nail, in which it grows back misshapen or thickened.

Toenail fungus can spread to other toes if it isn't treated. If the discoloration is due to melanoma, it may spread elsewhere in the body.

How Are Black Toenails Diagnosed?

A healthcare provider can examine your toenail and will ask you about any recent injury, activities, and style of footwear. Depending on the symptoms, they may ask for tests for underlying conditions that can lead to a black toenail.

If they suspect a fungal infection, they can take a small sample of nail clippings and send them to a lab for analysis in order to determine the recommended treatment option.

How Are Black Toenails Treated?

If the black toenail is not causing you pain and less than half of the nail is black, there is no need to treat it. Over time, the nail will grow out and the discoloration will no longer be present. See a healthcare provider for evaluation if more than half of the nail is black due to trauma so they can check for a subungual laceration (a tear or cut).

If it's painful due to swelling or pressure, you can try home treatments, including:

• Elevating your foot
• Applying a cool compress

A healthcare provider can treat a black toenail due to trauma by making small holes in the nail to relieve the pressure and drain the blood, but it must be done within two days after the injury. They will use a special instrument. It is not painful because the nail doesn't have nerves.

If black toenail is caused by a fungal infection, treatments include both topical and oral antifungals. There are some over-the-counter (OTC) remedies and medications available, including ointments and soaks.

Topical prescription medications that you apply to the nail include:

• Penlac (ciclopirox)
• Jublia (efinaconazole)
• Kerydin (tavaborole)

Oral prescription medications include:

• Diflucan (fluconazole)
• Grisactin (griseofulvin)
• Sporanox (itraconazole)
• Lamisil (terbinafine)

You may have to use more than one medication and it may take months or even more than a year to cure the infection. The nail may grow back differently.

If you have another kind of infection, from bacteria or yeast, your healthcare provider can prescribe appropriate treatment, including antibiotic ointments or oral medication if necessary.

In the rare case of subungual melanoma, the treatment is usually surgical removal of the growth. If it has spread beyond the nail or toe, your healthcare provider will discuss treatment options with you.

How Are Black Toenails Prevented?

You can't always prevent black toenails, especially those caused by a sudden injury. However, there are steps you can take to reduce the likelihood of developing a black toenail. For example:

• Wear properly fitting shoes.
• Keep your toes dry and clean.
• Avoid wearing open-toed sandals, especially when working or walking in places where your toes might get stubbed or stepped on.
• Avoid exposing your feet to the sun.
• When applying sunscreen to your feet, make sure to include your toes.
• If you have an underlying condition such as diabetes, make sure it is well-managed.
  

Summary

A black toenail is often the result of trauma to the nail in which the injury bleeds and the blood pools under the nail. It should resolve on its own as the nail grows out. There are other causes for a black toenail, including fungal infections and ingrown toenails. Some medications and, rarely, cancer, can also cause a black toenail.

If the nail hurts after injury, a healthcare provider can drain the blood painlessly. For infections, antifungals and antibiotics that you apply to the nail or take orally can help. If a black toenail hurts, the discoloration has appeared gradually, or the discoloration spreads beyond the nail, call a healthcare provider.