If you’ve been running for a while, you’ve probably looked down at your feet post-run and noticed a black toenail staring back at you. It’s one of those things runners don’t always talk about, but it’s incredibly common. Some wear it like a badge of honor, while others cringe at the sight. Either way, it’s not exactly comfortable. So why does it happen, and more importantly, how can you keep your toenails from looking like they belong to a horror movie character?
What Causes Black Toenails in Runners?
Black toenails—also known as runner’s toe—happen when repeated pressure or impact causes blood to pool under the nail. It’s basically a bruise, but under your toenail. Here’s why it happens:
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Shoes That Are Too Small – If your shoes are too tight, your toes don’t have enough space, and they’ll keep slamming against the front with each step.
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Shoes That Are Too Big – On the flip side, shoes that are too roomy can cause your foot to slide forward, jamming your toes into the end of your shoe.
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Downhill Running – Gravity isn’t always on your side. Running downhill increases the impact on your toes as they push forward into the shoe.
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Long Runs – The longer you run, the more steps you take. More steps equal more micro-trauma to your toenails.
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Poorly Trimmed Toenails – Long nails get pushed into the front of your shoe, while nails cut too short can lead to pressure points that cause damage.
Will It Fall Off?
Maybe. If the blood underneath lifts the nail, it may eventually detach. It’s not always painful, but if there’s pressure building up, it can be uncomfortable. If it’s painful, you might want to see a doctor to drain it. Otherwise, the nail will either grow out or fall off and start fresh.
How to Prevent Black Toenails
You don’t have to accept bruised nails as part of the deal. A few small changes can make a big difference:
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Find the Right Shoe Size – Make sure there’s about a thumb’s width of space between your longest toe and the end of the shoe.
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Check Your Lacing – Try different lacing techniques to keep your foot secure and prevent it from sliding forward.
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Trim Your Toenails Correctly – Cut them straight across and keep them at a moderate length. Not too long, not too short.
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Choose the Right Socks – Moisture-wicking socks reduce friction, and some even have padding in key areas to protect your toes.
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Consider Your Terrain – If you’re doing a lot of downhill running, be mindful of how your feet are moving inside your shoes.
Need Help with Your Running?
Black toenails might seem like a small issue, but they can be a sign that something’s off with your gear or running mechanics. If you’re dealing with this (or any other running struggles), I’d love to help. As a coach, I work with runners to improve everything from form to training plans to strength work—all the details that help you run stronger and stay injury-free.