Why Your Toenails Are Turning Black (and How to Fix It)

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Black toenails are common among marathoners and other serious runners, but you don’t have to put up with them. Chances are, your shoe size is contributing to the problem. So here’s a guide to preventing black toenails and dealing with them when they do occur.

And yes, in case you were wondering, a black toenail can sometimes fall off. If it’s never happened to you, you’re probably absolutely disgusted right now. If it has—and I’ve been there—you know it’s not that bad and it grows back. But we’ll get to that in a second.

Why do toenails turn black?

Typically, a black (or blue or purple) toenail is just a bruise that you can see because your toenail is transparent. That’s what we’re going to talk about today. These bruises can happen suddenly, like dropping a weight plate on your toe, or they can happen when you stub your toes against the front of your shoes thousands of times per mile.

There are other reasons why a toenail may change color. If you’re unsure whether it’s a bruise or something more serious, have a healthcare professional examine you. These other reasons can include normal pigmentation changes that can occur over time, different types of toenail fungus, and even some types of skin cancer. A color change that extends beyond the nail, for example, is cause for concern, as is a dark spot that stays in place for months instead of growing out or fading. But generally, if you’ve been walking for miles and your toes are starting to turn black, the cause is obvious.

Choose your shoe size

Although bruised toenails are common among people who run a lot, they are by no means inevitable. If your toenails are constantly bruised, your shoes are probably too tight around the toes.

I got my first black toenails when I started training for a marathon, after years of never running more than 3-5 miles at a time. I had bought size 8 running shoes for my size 8 feet, and they had fit me just fine for all those years, until I increased my mileage. So when it came time to buy a new pair, I upgraded to an 8.5. My toenails stopped getting black, and as a bonus, I stopped getting blisters.

Your feet swell a little when you run, so it’s a good idea to buy shoes that accommodate this. You might think that this would cause your feet to slide around more in your shoes, but running shoes are designed so you can lace them around your instep while still having plenty of room around your toes. If you need a little extra help keeping your foot toward the back of the shoe, use that extra pair of lacing holes and attach a heel lock to fine-tune the fit.

Change your socks

If you run in thick socks, switching to thinner socks can save you some room. As a bonus, thin socks designed specifically for running will often make your feet less prone to blisters. Try Feetures or Swiftwick.

Cut your nails

Another way to keep your toenails from growing into the front of your shoes is to keep them trimmed. Cut them as short as possible (Also Short hair can also be itchy), and trim or file it frequently to keep it that way.

Paint them, maybe

The summer I had all these black nails, I started buying nail polishes in interesting colors. Bruises show through anything clear, but it was fun to experiment with dark colors, especially blue and purple.

I couldn’t find any expert consensus on whether or not it’s bad to keep bruised toenails painted. not It’s true that nails need to “breathe” (the tissues in our toes get their oxygen from our blood, not directly from the air), but in some cases, nail polish and the chemicals we use to remove it can contribute to drying out the nail, or they can simply make it harder to see if the nail underneath is healthy.

I will say that many runners paint their nails without any ill effects, but if you have doubts, you can also save the nail polish for special occasions. The dark color of the blue will eventually fade.

Seek medical attention if they are in pain

It is possible for blood to accumulate under a bruised nail to cause so much pressure that it causes pain. A doctor or other health care professional can pierce the nail to drain the fluid and relieve the pressure.

There are plenty of instructions on the internet on how to do it yourself, using a hot needle, a paper clip, or even a drill. Although some people have done it before, I do not recommend self-surgery. In any case, draining a toenail is indicated when the pressure of the fluid under the nail causes pain. It will not do anything for toenails that are painless or slightly painful after turning black from a slight bruise.

I can’t wait for them to drop

This is the funny/gross part: injured nails sometimes fall off. Sometimes they turn black and SO fall off, but you can also have nails that fall off without visible bruising, or vice versa.

It’s less gross than it sounds, because a new nail is starting to grow under the old one. You may not even notice what’s happening until the new nail is almost in place. One day, you’ll go to trim your nails and notice that one of them lifts easily: that’s the older, top nail getting ready to come out.

This transition period can be tricky, and you have two choices. First, if the nail is still mostly attached, use a bandage or tape to cover the toenail, making sure the loose edges don’t get caught in your sock or the inside of your shoe. Since the new nail underneath is thin and may not cover the entire nail bed yet, keeping the old nail in place will help protect your toe.

The other option is to remove the old nail, which you can do as soon as you feel it’s a better option than gluing it in. Consider using nail clippers to do the job carefully (rather than holding on and hoping for the best), then use a file to smooth out any rough edges.