Black Toenail: Symptoms, Causes, and Treatment

If you notice a toenail becoming discolored and turning black, it's often due to injury that causes a bruise called a subungual hematoma. There can be other reasons for discoloration, however, and black toenail can be painful.

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

Photographer, Basak Gurbuz Derman / Getty Images

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:

If the area becomes infected, you may note:

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.

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

Trauma resulting in a subungual hematoma is the most common cause of 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.

If you're a runner or walk a lot, you may have "runner's toe," a form of subungual hematoma. Momentum causes your toe to bump or rub against your shoe as you move. Your feet may also swell during exercise, which can create more pressure. It often affects the second or third toe.

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 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.

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.

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.

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:

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.

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

A healthcare provider can treat 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 the discoloration covers more than half the nail, if the nail is beginning to separate, or if the injury is severe, your healthcare provider may recommend removing the nail. They will numb the area first so that the procedure isn't painful.

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:

Oral prescription medications include:

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.

Certain factors can increase the risk of developing black toenail. These include:

Complications from black toenail can include permanent damage to the nail, in which it grows back misshapen or thickened. If the discoloration is due to melanoma, it may spread elsewhere in the body.

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 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.

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:

With 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.

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 black toenail, including fungal infections and ingrown toenail. Some medications and, rarely, cancer, can also cause 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.

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By Nancy LeBrunIn addition to her extensive health and wellness writing, Nancy has written about many general interest topics for publications as diverse as Newsweek, Teen Vogue, abcnews.com, and Craftsmanship Quarterly. She has authored a book about documentary filmmaking, a screenplay about a lost civil rights hero, and ghostwritten several memoirs.