The black toenail: newbies fear them, pros welcome them like a badge of courage. While they're not the most aesthetically pleasing bi-product of long-distance running, they're a normal result of upping your miles, and Dr. Douglas Comeau, DO, CAQSM, FAAFP, medical director, sports medicine at Boston Medical Center and the Ryan Center for Sports Medicine at Boston University, answers your most common questions, so you can rest easy (when you're not running, of course).
What causes them?
Dr. Corneau says there are two causes of a black toenail. The first is a sub hematoma, which is caused by a blow to the toe and bloodflow pools underneath the nail bed. But that's probably not why *you* have the BT. You, my friend, have/will have/have had what's also known as "runner's toe."
Increases in running volume, particularly training for a marathon or other long distance, are the culprit. The reason? "A major increase of a forward motion means more friction and more capillaries will burst," Dr. Corneau explains. "As pressure builds, blood pools underneath the nail bed." Dr. Corneau also cites biomechanical issues as a culprit, such as toes to lifting up against the shoe or gripping too tightly. Frequent downhill running can push the toes against the end of the shoe, too.
How do you prevent them?
Unfortunately, Dr. Corneau says there's no way to 100% eliminate the possibility of black toenails, especially if you're training. Make sure your shoes fit properly, with enough room in the toe box. Major mileage in hot weather will increase the chances of a BT, as your feet tend to swell. But really, this Tribe is tough and driven. We won't let our training and race schedules be driven by the temperature or season!
How do you treat them?
Most black toenails can go untreated. "The nail bed regenerates in about threes months," Dr. Corneau says. A severely damaged BT will fall off once a new, fresh toenail grows underneath, so once the pain wears off, it's simply an aesthetic issue. But if it's extremely painful, you can visit your doctor or podiatrist, who can perform a decompression and drain the liquid underneath the nail bed to relieve the pressure and pain. Dr. Corneau, who admits he has self-drained before (remember: licensed professional), says the worst thing you can do is DIY it at home in a non-sterile environment. Short story: If it's unbearable, head to the doctor.
Can you cover them up?
We've all wondered is a nice coat or two of nail polish can conceal a black toenail without hindering the healing process. Dr. Corneau says paint away. "The nail's already dead; it's not healing," he explains. "You're simply waiting for it to fall off naturally."