Black Toenail: What Causes It and What to Do About It

Medically Reviewed By Megan Soliman, MD
Was this helpful?
1

Black toenails have various possible causes. Some causes are temporary and resolve on their own, while others are serious and need medical treatment. Read on to learn more about what causes black toenails and what to do about them.

Overview

A person painting their toenails
Jayme Burrows/Stocksy United

Toenails can discolor for various reasons, including infections, injury, cancer, and other medical conditions. Some causes are mild and temporary, while others can be serious and need prompt medical care.

Nails are an important indicator of your health. Typical nails are smooth, without cracks or tears, and free of discolored spots or streaks. Discolored nails can be a symptom of a health condition.

If you have a black toenail with bleeding, pus, or severe pain, contact a doctor immediately for an evaluation.

Causes

Below are some possible causes of black toenails.

Fungus

Fungal infections in the toenails commonly appear yellowish or brown but may appear as black patches or streaks under the nails. Nail thickening often occurs due to accumulating debris in the nail layers.

Because black toenail fungus can appear similar to cancerous melanoma, it is important to have a doctor check black linear streaks. The presence of multicolored areas of brown or yellow alongside the black color can indicate a fungal infection rather than melanoma.

Medications

Some medications can cause black pigmentation of nails. These include:

  • chemotherapy agents
  • antimalarial medications
  • biological medications

Typical pigmentation

According to experts, people with darker skin tones may be more likely to have dark pigment in their nails. The discoloration may increase as a person ages.

Injury

Any injury to the toe that causes bleeding underneath the nail, or a subungual hematoma, can lead to a black toenail. If you drop something on your foot or accidentally kick a hard object, like a piece of furniture, a bruise will form beneath the nail.

Pressure due to bleeding under a nail can cause pain. In severe cases, bleeding under the toenail may separate the nail from the nail bed, and the nail may fall off.

Black toenails can also result from repeated injury to the nail. Runner’s nail is a black toenail that occurs due to repeated contact between your toe and the inside of your shoe while running.

Melanoma

Melanoma is a type of cancer that happens when cells that produce melanin begin to grow unmanageably. Melanoma under the nails is also called subungual melanoma. When this type of melanoma develops in the toenails, it most commonly affects the big toe.

Other symptoms that may indicate melanoma include:

  • pigment on the skin next to the nail
  • splits or cracks
  • bleeding
  • pus
  • pain

Contact your doctor if you have any of these symptoms.

Learn more about the difference between subungual hematomas and melanoma.

Other medical conditions

Additional conditions that can cause toenails to turn black include the following:

Treatments

The treatment for your black nails will vary, depending on the cause. Some black toenails may only require monitoring and time, while others may need extensive care.

Treating fungal infections

Fungal infections in the toenails can require multiple treatments to resolve.

Your doctor may choose to treat the infection with topical medications, oral medications, or a combination of both. If the infection is severe, you may need surgery to remove all or part of the infected nail.

Ongoing infection may cause thickening and lifting of the toenail away from the nail bed. Use all medications exactly as your doctor directs, and keep your appointments.

Treating injuries

Most of the time, you can treat a toenail that turns black from an injury by resting and elevating your foot, along with ice and compression. You can ask your doctor about taking over-the-counter pain relief medication as well.

In cases of severe pain due to blood pooling under a nail, your doctor may carefully puncture the nail to drain the blood and relieve the pressure. A doctor may need to remove severely damaged nails.

Treating melanoma

Detecting melanoma early increases the likelihood of treatment effectiveness. Depending on the stage of your melanoma, you may receive one or a combination of the following treatments:

Learn more about treatments for melanoma.

Treating underlying disease processes

If you have a medical condition causing black toenails, work closely with a doctor to monitor and manage your condition. They will develop a treatment plan for your specific condition and situation.

Complications

Some complications that may accompany black toenails include:

  • pain
  • infection
  • permanent damage to or loss of the nail

Outlook

The outlook for a black toenail depends upon the cause. A mild injury, such as a runner’s toe, may resolve on its own with rest. More serious causes will have variable outcomes.

You can help heal a black toenail and prevent complications by following a doctor’s instructions carefully, monitoring affected and unaffected toes, and notifying the physician of any changes.

New nail growth will take several months to replace older, discolored nails.

Prevention

You can prevent injury to the toenails by wearing closed-toe shoes for activities that may increase the likelihood of an injury. Playing sports or working in jobs like construction or manufacturing require specialized footwear designed for those purposes.

If you are routinely in a locker room or similar environment, wear nonslip rubber shower shoes as a barrier between your feet and the floor. This may help prevent toenail fungus.

Experts recommend that people with diabetes and other circulatory conditions carefully protect and care for their feet due to the risk of nail damage and nonhealing wounds.

Subungual melanoma is serious, and although it is relatively rare, it can spread rapidly. If you wear nail polish, examine your toenails between pedicures for black areas. Notify a doctor of newly occurring black toenails, especially if they occur with pain, bleeding, or pus.

When to see a doctor

Because black toenails can potentially signify a serious condition, it is important to contact a physician if one or more of your toenails turn black. They can evaluate your overall health, identify the cause, and prescribe appropriate treatment.

If black toenails occur with pain, bleeding, or pus, it is essential to contact a doctor without delay.

Summary

Black toenails have various causes. Medical conditions such as diabetes, injury to the nail, or cancer can all lead to black toenails.

If you develop a black toenail, get medical attention. Your doctor can help you pinpoint the cause and create an appropriate treatment plan.

Was this helpful?
1
Medical Reviewer: Megan Soliman, MD
Last Review Date: 2022 Dec 7
View All Skin, Hair and Nails Articles
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Melanoma skin cancer. (n.d.). https://www.cancer.org/cancer/melanoma-skin-cancer.html
  2. Melanonychia. (2017). https://dermnetnz.org/topics/melanonychia
  3. Mole, R. J., et al. (2021). Subungual melanoma. https://www.ncbi.nlm.nih.gov/books/NBK482480/
  4. Nail fungus. (n.d.). https://www.aad.org/public/diseases/a-z/nail-fungus-overview
  5. Ohn, J. et al. (2017). Dermoscopic patterns of fungal melanonychia: A comparative study with other causes of melanonychia. https://www.jaad.org/action/showPdf?pii=S0190-9622%2816%2930632-6
  6. Pingel, C., et al. (2022). Subungual hematoma drainage. https://www.ncbi.nlm.nih.gov/books/NBK482508/
  7. Singal, A. et al. (2020). Melanonychia: Etiology, diagnosis, and treatment. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7001389/