Black Toenail

You've Injured Your Toenail, It's Turning Black, Now What?

Black Toenail
Black Toenail. anayah © Deposit Photos

At the end of a long walk or run, you may notice that a toenail has turned black or gray, and it may be swollen under the nail. What happened? What's going to happen? You are getting a black toenail, also known as a subungual hematoma - bleeding under your toenail.

What is a Black Toenail - Subungual Hematoma?

As you walk or run, your foot slides forward in your shoe, banging your toes against the top, front, and sides with each step.

Your feet also swell during a walk or run and get compressed by your socks and shoes. That pressure and impact can damage your toenail beds, or create a blister under the toenail itself. When this happens, the extra blood and fluid cause your toenail to separate from the toenail bed. The blood colors the toenail black. Your toenail will probably continue to change colors during this process.
Photos of Black Toenail

Is Your Black Toenail Painful?

If there is a blister under the toenail, you may see the toenail raised and it may be swollen and painful. It is best to try to ignore this for 24 hours and see if it goes down by itself. No treatment is needed unless the nail is raised and painful after 24 hours. Nature will take its course and you should simply leave it alone.

If the nail is still raised and painful after a day, you may want to see a doctor. If your black toenail happened due to an accident where your toe was crushed, you should see a doctor so it can be checked for other injury.

Treatment for a Black Toenail

There is no need to drain a black toenail that isn't raised and painful. If the problem is simply a pool of blood under the nail and it continues to be raised and swollen, then a doctor would relieve the pressure by poking a hole in the nail - trephination. Although it's preferred that a professional does this, it is something that some people do at home themselves. If you have diabetes, you must seek medical help rather than draining it at home as an infection can have serious consequences.

You can see self treatment described by marathon coach Jeff Galloway and in the book "Fixing Your Feet: Prevention and Treatments for Athletes" by John Vonhof, Wilderness Press, 2011.

Monitor Your Toe for Signs of Infection

If the toe continues to be swollen and red after draining the excess fluid, see a doctor to ensure it has not become infected. Take infection seriously. If it continues to hurt or the pain increases, this is a bad sign. Toe infections can lead to blood infections, gangrene, and worse, especially if you have diabetes.

Will I Lose My Toenail?

The short answer is - yes. It will take a few weeks or months, but as the toenail continues to grow, eventually it shoves out the damaged, blackened toenail. The black toenail is raised off of the toenail bed, and underneath it is often the healthy remainder of your toenail. Your black toenail will gradually loosen from the sides and you will be able to trim it away.

When Will My Toes Be Pretty Again?

If pretty toes are important to you, you can paint the black toenail or even the new thin toenail, or the bare skin. Most people won't notice the difference if you use a darker shade of polish. Full replacement of your toenail takes about 3 months, and the new toenail will often be a bit wavy, thin in some areas and thicker in others.

After 4-5 months your toenail should be back to normal.

How Can I Prevent Black Toenail?

Your running or walking shoes and socks must fit correctly. Your feet swell a full shoe size over the course of a longer run or walk, and your toes must have someplace to expand into. The toebox must be wide enough, yet not too wide or your toes will bang around in it. Getting fit at a technical running shoe store in your area is your best method of ensuring your shoes fit correctly.
Getting Shoes Fit Right

The trauma of toes banging into the shoe can be eliminated by proper lacing of your shoes to keep your heel in the heelbox rather than letting the foot slide forward in the shoe with each step.

See: Shoe Lacing to Prevent Heel Slippage


Subungual Hematoma, American Osteopathic College of Dermatology, accessed 4/4/2016.

"Fixing Your Feet: Prevention and Treatments for Athletes" by John Vonhof, Wilderness Press, 2006.

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