Recently a blog follower wrote to me and asked what to do about her black toenail.  The toenail had been black for some time but she was now worried that it was going to fall off.

Black toenails are not an uncommon *injury* for runners and walkers.  I label them an injury because they are caused by trauma to the nail bed.

Let’s first address what to do if this happens to you:

1.  After your run sterlize a needle and poke gently below the nail.  Drain the blood and excess fluid that has accumulated underneath and is most likely causing uncomfortable pressure.
2. Dip your toe or toes in hydrogen peroxide to help kill some of the germs.
3. Leave your toe alone and let it heal.

The toenail will most likely eventually fall off.  It’s important not to rush this process, as the outer nail protects the new nail that will grow underneath.  When its getting close to the time that your nail will fall off you may notice that it becomes raised, this is normal.  Again, do nothing and wait for it to fall off on it’s own.

When the nail comes off you might notice that the nail underneath is anything but pretty.  It may be thin, bumpy, or it might not even be there at all.  Time is the only thing that will help your nail take on a more normal look. 

Lastly you might not want to paint this toenail when it’s going through the healing process.  Nails inevitably absorb some of the nail polish painted on them and the last thing a new nail needs is chemicals to pollute it.

Now let’s address what can be done to prevent this in the future:

Make sure that your running shoes are the correct size.  Running shoe manufacturers, such as Saucony, design their shoes with extra room in the toe box.  If your toes are smack dab up against the edge of the shoe, the rest of your foot is not aligned properly.  Not only can this cause black toe nails but a whole host of other problems.

Allow at least a thumb nails width of room between the end of your longest toe and the front of the shoe.  I wear a size 8 in women’s shoes and I now wear a size 9 in my Saucony running shoes.  When you run your feet swell.  If there is no extra room in your shoe then your foot is restricted.  The pressing and rubbing of your foot against the shoe will cause your toe trauma and cause the toe nail to turn black.  This can also be one of the causes of blisters.

I say allow the extra room from your longest toe, because for some of us, me included, your longest toe is not your biggest toe.  This is called a Morton’s Toe.  When I measure my shoe, I measure from my 2nd toe.  While sometimes this may feel like I have too much room in my shoe, I promise you after a 20 mile run there is NO extra space in there.

Consider also the type of sock you plan on wearing with your shoes when purchasing the correct size.  In the winter runners often switch to thicker socks for warmth.  This may mean that during the summer time you wear a 9.0 but during the winter you wear a 9.5 in order to allow the proper amount of extra room.  Again the extra room is not something that is there for fun.  If you don’t allow the room, then your foot might not be properly aligned in your shoe.  The first sign you are in the wrong size shoe is if your shoe size for your every day shoes is the exact same size as your running shoe.

Another cause of black toenails is doing too much too soon.  It takes time for your body to adjust to the increased mileage of training for new distances.  This is why I often do not recommend that someone train for a marathon the first year they start running.  Each time you run a certain distance your body learns to adapt to that distance.  The more times you have run a certain distance, the greater the adaptation becomes.  If you have been consistently training for years for the half marathon distance you probably will not experience as many, if any, black toenails, compared to someone who just took up running and is now training for the 1/2 distance. 

The last main cause of black toenails is speed.  The faster that you run the quicker the motion of your foot swinging forward is.  This increased motion, such as during a race, can cause your foot to hit the front of your shoe at a more rapid than usual rate.  I had the worst black toenails I have ever experience after running B&A Marathon.  They were in part due to the fact that I was wearing racing flats, something I do not recommend for most runners tackling the marathon distance, and because I was running faster in those shoes longer than I had ever run before.  If you ran your local 5K this weekend, PR’ed and got a black toenail, that means you were going faster than your body is used to – Congrats.  Wear that black toenail like a badge of honor.


  1. shellyrm aka jogging stroller mama says:

    Summer is over. Who need pretty toenails anyway. 😉

    Great info. It sure does scare new runners when they had their first black toenail.

  2. Runners Fuel says:

    Thanks for the info.

  3. Momma K and her Krew says:

    I have 2 missing and 2 black-turning white going to fall off soon toenails. I just wonder how to make them presentable. They look crusty and gross…just in time for a trip to Mexico. Any idea on how to atleast make them not look diseased? I did too many hills in too small of shoes with crappy socks–the trifecta of black toenails.

  4. Karen the "Hungry Mom" says:

    im so jealous. i want a black toenail. i feel like im not a real runner because Ive never had one :)

  5. Forward Foot Strides says:

    Thank you for this! I'm totally guilty of painting over my aesthetically unappealing black toenails. I should stop that now that sandal season is over.

  6. Please, god – don't let me get a black toenail!

  7. Mile Posts by Dorothy Beal says:

    Momma K – I would say to just exfoliate your feet, lotion them up and make the non-blackened ones presentable. Seriously I feel your pain, but it's best to just leave them alone and let them heal. A nude nailpolish color will also help to not draw anyones gaze toward your feet!

    Hungry Mom – NO you do not want a black toe nail :) They are no fun. Up until recently I was really proud to say I had never gotten one.

    Forward Foot – I don't think it's too bad painting over the original nail that has turned black. I'd worry more about the new nail coming in and just leave that one alone when the other one falls off! No one can hold it against a girl for wanting her toes to look nice 😉

  8. This is a very nice post, so informative and interesting. Thanks for sharing such a great post.

  9. Rebecca Samson says:

    Such a good post! I'll never forget the day I lost my first toe nail. It never turned black just fell off. Ugh yuck!

  10. turnerlifearound says:

    thank you dorothy! i am going to self diagnose and say it was too much too fast but ive seen the negative affects (besides my disgusting toe) that this has…thanks for all the great information and experience :)

  11. Thanks for the info. I have experienced this in the past.

  12. great post! the last time i lost a toenail (after shamrock this spring) it turned a pretty shade of lavender instead of black. it made it a little more bearable during the summer months!!

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