What Causes Black Toenails

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Black toenails are a common condition that can be caused by a variety of factors. They occur when the blood underneath the toenail turns black, either due to trauma, repeated pressure, or a fungal infection. 

In this article, we will explore the most common causes of black toenails and discuss the treatments available to address this issue.

What Are Black Toenails?

Black toenails refer to a condition where the toenail turns black in color, usually as a result of bleeding underneath the nail. The cause of the bleeding can vary, but is often due to trauma, repeated pressure, or a fungal infection. Black toenails can be unsightly and potentially painful, and it is important to seek proper treatment to address the underlying issue.

What Causes Black Toenails?

Black toenails are a common condition that can be caused by various factors. These can range from physical trauma to the toenail, repetitive pressure on the nail, to underlying medical conditions such as fungal infections. 

In this section, we will explore the different causes of black toenails, including the most common ones, to give you a better understanding of what might be causing your black toenail. By understanding the cause, you can make informed decisions about the best course of treatment.

Poor Fitting Shoes

Poorly fitting shoes can be a common cause of black toenails. Shoes that are too tight or too loose can put excessive pressure on the toenails, leading to trauma and bleeding underneath the nail. 

Shoes that are too narrow or too short can also cause the toes to rub against the front of the shoe, leading to repeated trauma to the toenail. High-impact activities such as running or jumping can also put additional pressure on the toenails, making them more susceptible to blackening. 

It is important to wear shoes that fit properly and provide adequate support to prevent black toenails from forming. This means finding shoes that are comfortable and offer enough room for the toes to move freely, without rubbing against the front of the shoe. 

If you are experiencing black toenails as a result of poor fitting shoes, it is best to switch to a different type of shoe or consider getting custom orthotics to help distribute pressure more evenly.

A Toe or Foot Injury

A toe or foot injury can also be a cause of black toenails. Trauma to the toenail, such as from a direct impact or from dropping a heavy object on the foot, can cause bleeding underneath the nail and lead to the nail turning black. 

In addition, repetitive stress injuries such as stress fractures or plantar fasciitis can also cause black toenails by repeatedly putting pressure on the nail. If you suspect you have suffered a toe or foot injury that has caused your black toenail, it is important to seek medical attention. Your doctor can perform an examination and possibly imaging tests to determine the extent of the injury and recommend the best course of treatment. 

This may include rest, immobilization, physical therapy, or other interventions to help manage your symptoms and promote healing. In some cases, surgery may be necessary to correct the underlying injury.


Melanoma is a type of skin cancer that can affect the toenails. Although rare, melanoma of the toenail can cause a dark or black discoloration of the nail, which may also have a irregular border or changes in the shape or texture of the nail. Other signs of toenail melanoma may include a dark streak under the nail, a black or brown band across the nail, or a sore or painful area near the nail. 

If you suspect you may have toenail melanoma, it is important to see a doctor as soon as possible. Your doctor can perform a biopsy to confirm the diagnosis and determine the best course of treatment. Early diagnosis and treatment of toenail melanoma is critical for a good outcome, as the cancer can spread to other parts of the body if left untreated. In severe cases, surgery may be necessary to remove the affected nail and surrounding tissue.

Toenail Fungus

Toenail fungus, also known as onychomycosis, is a common cause of black toenails. Fungal infections can cause the nail to become thick, brittle, and discolored, often taking on a dark or black appearance. Toenail fungus can develop as a result of a fungal infection in the nail bed, skin, or surrounding tissue. 

Risk factors for toenail fungus include poor hygiene, a weakened immune system, warm and moist environments (such as in socks and shoes), and previous nail injuries. Toenail fungus is often treated with antifungal medications, either in the form of topical creams or oral tablets. In severe cases, removal of the affected nail may be necessary. 

To prevent toenail fungus from developing, it is important to maintain good foot hygiene and to avoid sharing nail clippers, files, or other tools with others. Additionally, wearing shoes or sandals in public areas, such as showers or pools, can help reduce your risk of fungal infections.

Other Certain Medical Conditions

There are certain medical conditions that can also cause black toenails. Some medical conditions include:

Diabetes: Diabetes can cause poor circulation in the feet and legs, leading to a decrease in blood flow to the toes. As a result, the toenail can turn black due to a lack of oxygen and nutrients.

Peripheral Artery Disease: Peripheral artery disease (PAD) is a common condition that affects the vessels in the legs and feet. It can lead to a lack of blood supply to the lower extremities, resulting in blackened toenails.

Autoimmune Disorders: Certain autoimmune disorders, such as lupus and rheumatoid arthritis, can cause inflammation in the nails and surrounding tissues, which can lead to discoloration.

Hormonal Imbalances: Hormonal imbalances, such as those occurring during pregnancy, can cause the toenail to darken.


In conclusion, black toenails can have a variety of causes, ranging from physical trauma to underlying medical conditions. 

Some of the most common causes of black toenails include poorly fitting shoes, toe or foot injuries, toenail fungus, and certain medical conditions. It is important to identify the cause of your black toenail in order to determine the best course of treatment. 

If you are experiencing black toenails, consider seeking medical attention to receive a proper diagnosis and to ensure prompt and effective treatment. By working with your doctor, you can take steps to manage your symptoms and promote healing, helping to ensure healthy and pain-free feet.

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This blog post is for educational purposes only and does not constitute medical or other professional advice. Your specific circumstances should be discussed with a healthcare provider. All statements of opinion represent the writers' judgement at the time of publication and are subject to change. Phoenix and its affiliates provide no express or implied endorsements of third parties or their advice, opinions, information, products, or services.

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