A friend of mine read that you’re supposed to drain the blood from underneath a black toenail by “burning” a hole in the nail with a hot paper clip or needle. Maybe I’m being too squeamish, but that sounds scary and extreme to me. Isn’t it better to leave the nail alone, and if you have problems to see a doctor?
—Jennifer

Jennifer, there are several causes of black nails in runners and non-runners, subungual hematoma being the painful counter that requires a hole in the nail to decompress the blood pool and relieve the pressure causing the pain. Hematomas are generally the result of trauma to the nail area (like dropping a heavy object on the toe) that in turn causes blood to accumulate under the nail. The pool of blood produces pressure and often severe, throbbing pain. Decompressing the hematoma relieves the pain. You could try to burn or drill through the nail to relieve the pain, but this is a procedure often best left to your physician.

If you really want to do it at home, I suggest using a very small-diameter drill bit and rotating it between your thumb and pointer finger. (Do not use a power drill, as you might end up with a hole through your toe!) The trick is to slowly cut through nail but not to cut into the skin below the nail. In the office, I routinely burn holes through nails with a hand-held electric cautery device. The gush of blood cools the heating element so the skin below the nail does not burn.

The much more common cause of black nails in runners, however, is bruising or slight bleeding under the nail from repetitive trauma of the top of the shoe striking the nail with each step or the toe sliding forward into the end of the shoe. I see this commonly in runners training for marathons and in highly competitive runners training for shorter distance races but at high intensity and volume. These nail injuries are generally not painful, although sometimes the nails do thicken. They will heal when the training volume and intensity decreases, and the repetitive trauma ceases. A shoe with adequate toe room will also help in some cases. Drilling a hole will not help this problem and hot cautery will really hurt.

There are other causes to consider. One is fungal infection that can thicken the nail and sometimes turns the nail dark, almost black. This can be treated with oral antifungal medications over six months time. The thickened nails can be painful but generally do not throb.

Finally, a black spot under the nail could be a melanoma. If you have a dark spot under the nail that does not go away, have your physician check it.

One tip regarding nail polish: It is tempting to hide black nails with polish. Nail painting looks great, but it does not allow the nail to breathe and you may risk losing it altogether. It is certainly OK to polish the nails for special occasions, but I do not recommend leaving the polish on for the summer. This is true for you guys out there, too.

Cheers,
Bill