What Causes a Toenail to Turn Black?

A black toenail, often referred to as a "subungual hematoma," occurs when there is bleeding or bruising underneath the toenail. It typically happens due to trauma or injury to the toe, such as stubbing it or dropping something heavy on it. The blood trapped beneath the nail causes it to turn black or dark in color as it dries and clots.

This article will review black toenail symptoms, potential complications, treatment options, prevention, and when to contact a healthcare provider.

Black Toenail Symptoms

There are a few symptoms that may characterize or accompany black toenails. These typically include:

• Dark discoloration under the nail
• Pain or discomfort
• Swelling and bruising
• Possible bleeding or hematoma
• The nail may become brittle or loose

What Does a Black Toenail Mean?

The presence of a black, purplish, or brownish hue beneath or around a toenail typically stems from toenail trauma. This can often occur following a toe injury, such as stubbing the toe or dropping an object into it. This discoloration arises as a result of blood pooling or bleeding beneath the nail, and it can affect either the entire nail or a localized area on the nail.

Runner's Toe

When the second or third toenails become black, it may be due to a condition referred to as "runner's toe." This condition can be triggered by the nail being too long and the shoe either being excessively roomy or excessively snug.

In cases of oversized shoes, while running downhill, the foot may slide, causing the nail to become entangled at the intersection of the toe cap and the toebox. Conversely, overly tight shoes can pinch and compress the nail, leading to bleeding between the nail plate and the nail bed.

Malignant Melanoma

A more serious underlying cause of black toenails is malignant melanoma. However, this condition is rare.

Subungual melanoma is a highly dangerous form of cancer, often manifesting as a dark line running along the nail's entire length. The term "subungual" refers to something that occurs beneath the nail.

Given that early detection and treatment of melanoma significantly improve prognosis, it's crucial for any black toenail to be assessed by your healthcare provider to rule out this potential cause.

Rare Causes of a Black Toenail

Very uncommon sources of black toenails may also include:

• Fungal or bacterial infections
• Persistent ingrown nails
• Systemic health conditions affecting the body as a whole
  

Possible Complications

Complications caused by a black toenail are dependent on its cause. However, in most toenail injury cases, a new nail replaces the discolored and damaged nail over several months. In this case, there is no need for further treatment.

In a case where more than 50% of your nail is black from bleeding beneath the nail, you should see your healthcare provider to rule out fractures or lacerations of the nail bed, which could warrant removing the nail and sutures to repair the laceration.

One important concern to keep in mind is the potential for injury to the cells responsible for nail regeneration, known as the nail matrix. If the nail matrix sustains damage, it can lead to improper nail growth or, in some cases, a failure to regrow a new nail.

When to Contact a Healthcare Provider

There are a few reasons to seek medical attention if you or a loved one sustains subungual hematoma due to injury, including:

• Uncontrollable pain
• Significant injury to the nail base
• Bleeding that does not stop

If you have any of the following nail symptoms or conditions, contact your healthcare provider, as they may signify a more serious health condition:

• Blue nails: a lack of oxygen in the blood can cause a bluish tint to the skin and nails called "cyanosis." This may be caused by a heart or lung health issue.
• Clubbed nails: when the nails change and curve downward like an "upside-down spoon." This may occur due to health disorders that affect the oxygen levels in the blood.
• Horizontal ridges: Also called "beau lines," and can be caused by illness or lack of nutrition."
• Pale nails: Also called "white nail syndrome." May be caused by arsenic poisoning or another more serious health condition.
• Pitting in the nails: Small depressions or crumbling of the nails.
  
• Ingrown nails: When the end of the nail grows back into the skin. Complications include infection.
• Distorted nails
• Painful nails
  

If you notice a darkening of the cuticle, this may be a symptom of a condition called "Hutchinson sign." It is essential to seek immediate medical attention from a healthcare provider as this could indicate a more aggressive form of melanoma.

How Are Black Toenails Diagnosed?

First, you will need to make an appointment with your healthcare provider for an assessment. This typically involves a thorough examination of your nails and a discussion about your specific symptoms. Your provider may inquire about potential causes, such as recent nail injuries, consistent exposure to moisture or chemicals, or any habits like frequent nail picking that could contribute to nail issues.

To further investigate and diagnose a black toenail, various diagnostic tests may be ordered. These may include:

• X-rays to evaluate the bone structure beneath the nail
• Blood tests to assess for any other health conditions or infections
• Microscopic examination of nail samples or the nail matrix in a laboratory setting

These diagnostic steps help the healthcare provider pinpoint the precise cause of your nail problem and determine the most appropriate course of treatment.

How to Treat Black Toenails

Typically, treatment for a black toenail due to runner's toe or other injury involves a combination of the following:

• Rest
• Ice
• Elevation, and
• Gentle compression applied to the affected finger or toe

Your healthcare provider may also recommend over-the-counter (OTC) pain medication as necessary to alleviate discomfort.

Applying ice and elevation helps reduce swelling and pain, but it's essential to avoid direct contact between ice and the affected nail to prevent further injury. Instead, it's recommended to wrap ice in a cloth towel before applying it to the affected area. Compression can also be beneficial in reducing bleeding beneath the nail.

In more severe toenail injuries, your healthcare provider may recommend alleviating the pressure from the hematoma using a technique known as trephination. This procedure involves the use of a sharp instrument to puncture the nail, allowing the trapped blood to drain, which effectively reduces discomfort.

It's important to note that regardless of the treatment approach, the body will naturally reabsorb the hematoma, and a new nail will eventually grow out. Typically, this process takes approximately six to nine months for the nail to fully regenerate.

How to Prevent Black Toenails

Sometimes, it may be difficult to prevent a black toenail, such as in the case of an accidental injury such as stubbing your toe or dropping a heavy item on it. However, you may want to consider the following to help prevent or minimize toenail injury:

• Wear properly fitted shoes, especially when running or doing aerobic activity
• Keep toenails trimmed and avoid sharp corners
• Protect toes during sports with appropriate footwear
• Maintain good foot hygiene to prevent infections
• Wear protective footwear when doing home improvement projects or any construction work

A Quick Review

Black toenails are typically caused by trauma and sports-related issues (such as runner's toe) and are less commonly caused by malignancies, fungal infections, or other systemic health conditions.

However, black toenails caused by injuries can be very painful, cause significant discoloration of the nail that can last up to nine months, and sometimes lead to permanent nail changes.

Treatment approaches may include rest, ice, elevation, and compression. More severe toenail injuries may require more invasive techniques like trephination to release trapped blood.

It is essential to seek medical attention in cases of severe pain, nail-base injuries, uncontrolled bleeding, and certain nail abnormalities.