For the past year and half, I have been doing really good with keeping all 10 of my little toenails.  I have had some amazing pedicures and my toes have been beautiful all summer! LOL! Well, then came training time for my 1/2 marathon this past August and at the same time, the heat has been unbelievable at times! Still, I was doing good until AFTER my running event ended.  Yes, you guessed it! 
I got . . ."THE BLACK TOENAILnailnailnail!"
Two to be exact!

If you are training for a long distant event, working, taking care of the kids or having fun hanging with your friends, sometime your toenails are the LAST thing that is on your mind (unless you are a shoe lover like myself and your toes must show!)!  You get out there and train like crazy, your shoes fit nice and snug.  It's all is good in the world of training, right?  Then, you start to feel it.  Your toes feel a little uncomfortable, bruised and even sore.  You know that in just a few weeks, you are going to lose a couple of your favorite little friends. . .UGH!!! 

Make sure your running shoe is 1/2 size bigger than
your street shoes.  You NEED the toe room!
Falling toe nails are common among long distant runners and if runners are not taking care of their feet, the nails are the first to go!  It starts with the rubbing of your toes against the front of your shoe.  A blood blister (isn't this disgusting) forms under the nail where it can not breathe and it takes a lot longer to heal.  In warmer weather, your feet swell more and you are more likely to get black toenails.  That makes sense for me because training for the AFC 1/2 marathon, there were many days it was hot and training was long. (Now you know why I am talking about black toenails, I lost two.)

How can you prevent black toenails? Well, first make sure that your running shoes are the correct size.  Running shoes should be 1/2 size bigger than regular street sized shoes.  Second, trim those nails! If you want long nails, let your fingers be the showcase and not your toes.  Third, make sure you keep your feet as dry as possible during your long runs. This has been a problem for me because I LOVE my cotton socks but wicking socks are better.  Cotton socks absorb the sweat and wicking socks keep the sweat away from the skin.  

When you are a victim of "THE BLACK TOE" just leave it alone.  Make sure you keep your feet and toes clean so that you will not get an infection.  Also, do not force the toenail to come off.  Let your nails do what they naturally do, grow and push the old nail out and off.  If you notice redness, swelling or possibly an infection see a doctor right away.

Happy Running and Happy Toes! 
(Embarrassing Running Problems / http://www.about.com)