Getting You Back On Your Feet

Black Toenail Syndrome

<< Conditions

Black toenail syndrome is a condition where one or more of the toenails turn black. The condition is very common in athletes, especially runners, and because of this, it is also called Runner’s Toes. Most distance runners develop it at some point, and it often means nothing more than you are training hard and perhaps should wear your black toenail like a badge of honor. The medical term for a black toenail is a subungual hematoma which simply means a bruise under the toenail. The black color of the nail comes from the dried blood. In spite of the name, a black toenail can be any color of a bruise ranging from black to blue to deep purple.

Black toenails are usually nothing to worry about and heal on their own. As the skin under the nail repairs itself, the black toenail ultimately falls off, and a new nail grows back. The old nail can take months to detach and the new nail can take 6 months to a year to grow in.


One way that black toenails develop is repetitive trauma caused by ill-fitting shoes. As your foot slides forward in your shoes step after step in an ill-fitting shoe, the toes shift around producing impact and friction problems between the toenails and surrounding tissues. Your feet also swell during exercise, and the toes can become compressed in the shoes causing additional areas of trauma.

Even with the perfect pair of running or walking shoes some people still have a chronic problem with black toenails. The very nature of endurance running is taxing on the feet. Even during a short 2-mile run or walk, you take over 4,000 steps. Each time your foot swings forward a little extra blood is forced into the toes. This extra blood becomes congested with no place to go, and the blood vessels under the toenail rupture. The result is an unsightly bruise or black toenail. Warmer weather also increases your chances of developing a black toenail. Warm weather causes the blood vessels to dilate allowing more blood to sling forward in the toes during running.


When considering treatment it is important to realize that there are other medical conditions that can cause a toenail to turn black that are more serious than a black toenail. A form of skin cancer called melanotic whitlow can cause a black toenail as well as certain types of tumors.

Most black toenails follow a fairly consistent and uneventful course. They turn black and fall or peel off after several months with no pain or complications. If, however, there is pain, swelling, or drainage associated with a black toenail a trip to the podiatrist is recommended. These symptoms could indicate an infection or more serious condition. Your podiatrist will take X-rays and perform an exam to rule out fractures or infection.

When a black toenail is very painful and is being treated soon after injury, your podiatrist may drill a hole in the nail to allow the fluid to drain out and alleviate the pressure that has accumulated under the nail. This procedure must be performed soon after injury before the blood and fluid coagulate. Another, and more common, procedure is to remove the entire toenail. This alleviates the pressure but also allows your podiatrist to inspect the nail bed for injury. Patients are often prescribed antibiotics for potential infection and pain medication as needed.


Generally speaking, black toenails are not painful. The tiny ruptured blood vessels only cause the unsightly appearance of the nail. However, if enough fluid builds up under the toenail the pressure can cause pain, swelling, and throbbing.


The best prevention of black toenails is to wear properly fitting shoes and increase your mileage slowly when running. Shoes should have one thumb's length of space between the end of your longest toe and the end of the shoe. Keep in mind that many runners buy their running shoes 1 size larger than their regular shoes. This is because your feet will swell during activity. It is also recommended to purchase shoes at the end of the day when your feet are their largest.  Keeping your toenails cut short also helps prevent black toenail syndrome. Wear absorbent socks during running to wick moisture away from your feet. If your feet become too sweaty during running they will tend to slide around in your shoes. This increases trauma to the foot and can cause black toenails.