Black toenails are a common malady among runners – especially those who run long distances. Black toenails result from repeated or constant rubbing of a toe against the front of your shoe. Black toenails are likely to occur if you run downhill a lot, during summer months when your feet swell, or running in wet shoes during winter and spring months.
The red or black color is a result of broken blood capillaries from constant pounding. Fluid and blood accumulate under the toenail, and the existing toenail eventually separates from the nailbed.
To prevent black toenails, make sure you’re wearing the right size of shoe. You should have at least a half of an inch of space between your toes and the front of the shoe when standing. You want to make sure you have plenty of room for your toes to move, but not so much that your feet slide around.
Other things that will help prevent black toenails is making sure you trim your toenails regularly – if they’re too long, they’ll rub against the front of the shoe. Also, make sure to wear socks that wick away moisture. Lacing your shoes tighter near the front of your shoe can help your feet from sliding, especially if you run downhill a lot.
If you do experience a black toenail, and you most likely will at some point, leave it alone! It will eventually fall off by itself, and a new one will grow in. Don’t force the old one off, and don’t try to relieve pressure under old nail by sticking a needle or other sharp object into it. If you notice redness or an infection at any point, see your doctor.
Full replacement of the nail takes about three to six months, and your new toenail will likely be thin and wavy. After eight to ten months and your toenail should be back to normal.