Black Toenails 101


I ran for roughly 10 years and kept all my toenails . . . until I didn’t. Although there are causes for black toenails (and we’ll get into that), much like chafing, it can be totally random.

What is a black toenail?
Black toenails can have many causes, but for runners, it’s usually caused by blood underneath the nail (technically a subungual hematoma). That blood puts a great deal of pressure on the toenail, and it can be very painful.

I was lucky: although I felt some pain, it wasn’t horrible, and I just assumed that it was a blister. It wasn’t until after I stopped running that it got really painful, but thankfully by the next morning it didn’t bother me that much.

What causes a black toenail?
The most common cause is repetitive trauma to the nail, either from the top of your shoe rubbing it or from your toenail slamming into the front of your shoe. In my case, I was wearing shoes I’d already worn in another half marathon (a steep downhill race, no less) with no issues.

The downhill race was much hotter, but also much less humid. Your feet do swell as you run, and more humid conditions will make them swell more — still, it was a pretty big shock to me when I took my shoes off.

How to treat black toenails
Follow Hippocrates advice: first do no harm. Leave it alone. Depending on the severity of the hematoma, there’s a chance that you’ll keep the nails — but most likely at some point the toenail will detach from the nail bed and you’ll lose it.

That’s what happened to me. I left it alone. I hoped I’d keep the nail, but I didn’t. It actually took almost a month before it fell off. It felt fine, was still black, and then one day it was just barely hanging on. I didn’t want to pull it, so I ended up just snipping the few remaining points that were hanging on.


What if it’s really, really painful?
It will be really, really painful the day it occurs; afterwards the pain should decrease rapidly. If it’s still really painful, or if you see signs of infection (redness, hot to the touch), then it’s time to seek a doctor’s help.

How can I avoid black toenails?
The first thing you can do is make sure your shoes fit properly. Even if you’ve been fitted for running shoes in the past, it’s not a bad idea to get fitted every year. Your foot can change — even gaining or losing weight can cause changes.

Keep your toenails trimmed — although don’t do it in the days right before a race — those sharp toenail corners can cause problems, too. A week or two before your race (depending on how fast your nails grow) make sure they’re clipped (I always do this!).

Increase training distance gradually so that your toes can adjust to the new distance.

Don’t run faster than your prescribed training paces and much like distance, increase pace gradually.

Will my toenail grow back?
In a word: yup. I was quite surprised that when my toenail finally detached, roughly a month later, there was already a new (tiny) toenail underneath it.

Black Toenails: Final Thoughts
Most runners who run longer distances will get a toenail at some point in their running career — maybe many. Some lucky runners will never lose one (I was in that camp for a long time!).

You know how they say pain is temporary and PRs are forever? The pain of a black toenail is also temporary. It may even signal a PR for you, or a new longer distance for you (sadly, neither was the case for me).

You can definitely take steps to avoid black toenails, but much like anything in life, they’re unpredictable, so forewarned is forearmed.


Linking up with Zenaida Arroyo and Kim @ Kookyrunner

This week I am also joining up with Running on Happy, Suzlyfe, Crazy Running Girl, and Coach Debbie Runs each week for the Coaches’ Corner linkup


15 thoughts on “Black Toenails 101

  1. So far so good. Never lost a toenail.

    I do buy my shoes pretty big – I wear a 7 shoe and 8.5 running shoe. I also make sure I have a wide toe box.

    Maybe that’s why. Maybe I’m just lucky.

    Another solution is always keep your toenails polished!! (I do.)

    No one one will ever know LOL

    Liked by 1 person

    1. As you know, I could have most of the same things until this happened. Sometimes no matter what you do, things just happen randomly.

      Since it was the middle of winter it’s not like anyone had to see it (except me) and quite frankly I don’t care what my toenails look like.


    1. You are lucky — pretty amazing considering how long you’ve been running. I ran 10 years before getting one, using the same shoes I’d already run a half in, blah blah blah. Life can be unpredictable!


  2. I’ve had two black toenails in my running “career”. Both when I was a much faster runner and both from sub-4 hr marathons. I don’t remember them being painful at all.

    Liked by 1 person

    1. Maybe yours weren’t as large as mine. It was very painful that day, but afterwards not so much.

      Obviously I am not a fast runner, nor was I running that much faster than normal for a half that day.

      I still suspect the socks but we’ll just never know.


  3. I’ve had 2 black toenails (at the same time), but didn’t lose either of them. The new nail coming in underneath grew together with the old nail so there was old, dead nail on top – kinda gross feeling! It took about 6 months to get rid of the old nail completely that way.

    Liked by 1 person

    1. I don’t do pedis at all. 🙂 Not even by myself. I’ve never had one and don’t really desire one! I do enjoy a manicure, but it’s been a really long time since I’ve had one, actually.


      1. You’re a jinx. I just lost my first toenail. I’m blaming this post 😀
        I could give up dyeing my hair and many other treats, I can’t see myself giving up pedis. The TLC is just too wonderful.

        Liked by 1 person

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