How to Prevent and Treat Black Toenails from Running

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It's common for runners, especially those training for long-distance running races, to get black or bruised toenails. Some long distance runners even consider getting a black toenail or losing a toenail a rite of passage. But, like other running ailments, it's possible to avoid getting black toenails. Here are tips to prevent and treat them.

Symptoms of Black Toenails

First, the toenail appears blackened and is painful.

The black color is blood under the nail (from a blister) drying up. The nail will usually fall off when a new nail eventually grows in.  Runners who are training for a marathon or do a lot of downhill running are the most likely candidates for black toenails because their toes are constantly rubbing up against the front of their shoes. You're also more likely to get black toenails if you run long distances in warmer weather because your feet swell more when it's hot.

Cause of Black Toenails

Black toenails are caused by constant hitting or rubbing of your toe against the front of your shoe. A blood blister forms under the nail, and the blister can't breathe, so it takes a lot longer to heal.

Prevention of Black Toenails

To prevent black toenails, make sure that you're wearing the correct running shoe size (at least 1/2 size bigger than your street size; you should have plenty of room in the toebox).

You should have one thumbnail's distance between your longest toe and the end of the shoe. Buy new running shoes at the end of the day when your feet are most swollen. Trim your toenails regularly, and keep your foot dry for as long as possible during your long runs. Sometimes a long toenail can hit the front of your shoe and lead to bleeding beneath the nail.

Be sure to wear good wicking socks, not cotton ones. Lace your shoes tighter along the front if you're doing a lot of downhill running.

Although black toenails do commonly occur when training in warm weather (when your feet swell), you should also be careful when running in cold weather. If you're wearing thick socks or two pairs of socks to stay warm, your running shoes may end up being too tight, putting you more at risk for black toenails.

Treatment of Toenails

Once you have a black toenail, it's best to leave it alone, as long as the pain is manageable. The pain is usually the worst on the first day and then lessens each day after. If it's extremely painful, a doctor can put a hole in the nail to relieve the pressure.

The damaged part of the nail is gradually pushed off, and a new nail will replace it. Don't try to force the old nail off -- it will eventually get loose and fall off on its own once the new nail grows in. If you're worried about how your toenails will look, it's OK to put nail polish on the black toenail and on the new nail coming in.

If at any point you notice redness and infection or the pain get worse, get it checked out by a health care professional.

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