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How to Treat a Bruised or Black Toenail from Running

Anyone who has been running for a decent amount of time has probably gotten the dreaded bruised or black toenail. I know I got my first ones after I ran a half marathon for the first time, and it took forever for them to grow back after they fell off!

If you’ve found yourself in this position, the article will cover everything that you need to know about black toenails, including what they are, what causes them, ways to treat them, and how to prevent them.

What Are Black Toenails?

Let’s start with the basics and define black toenails. The proper terminology is subungual hematoma although we all say black toenail. It is actually blood that collects under your toenail that has occurred from an acute or chronic injury.

Black toenails aren’t always black. They can be purple or brownish, but no matter what color it actually is, it’s clear that your nail is discolored. They can cover the entire nail or just a small portion of it.

How Bad Are Black Toenails, and Can They Get Infected?

Depending on the trauma to the toenail, black toenails can be mild – like something fairly tiny that doesn’t cause pain and is more cosmetic than anything. Or it can be severe with painful and large bloody blisters between the nail and nail plate.

And yes, they can get infected! The warm, moist environment inside your shoes is the perfect home for bacteria. If you have been running regularly with black toenails (especially if they are severe), you might be at risk for an infection.

What Causes Black Toenails?

There are actually several causes of black toenails, some that are more likely than others for runners. But it’s important to have a good idea of what caused your black toenails because some causes are serious and need medical attention.

Repetitive Trauma

This is the most likely cause for a runner. Black toenails can occur when your toenails are constantly taking a beating, typically the result from running on a regular basis and/or running long distances.

They can also occur as a result of wearing any type of ill-fitting footwear or loosely-laced shoes. This is especially bad if it’s coupled with running a lot. In particular, more downhill running means more bruised/black toenails as the foot slides forward.

If your toe box is too low, it will push down on the top of your nails as you push off from the ground. Also, shoes that are laced too tight (as opposed to too loose, which is also an issue) can compress the toenails.

In other words, if you’re putting undue stress on the toenails, that will cause repeated trauma and will lead to black toenails. Do it once, and it shouldn’t be an issue. However, if it’s a habit and routine, it will be.

One-Time Trauma

Unfortunately, there isn’t too much you can do to prevent black toenails from unexpected, one-time trauma. If you drop a heavy object on your foot, there’s a good chance that you’ll get a black toenail.

That being said, while it will take some time to heal, if you know that your black toenail is from dropping something heavy on it, you know that the cause is trauma and that it should be able to heal on its own. This means that it isn’t something more serious like melanoma.

Fungal Infections

Although we typically think of fungal infections as being yellow in color, which is often true, they can also turn a darker color if there is debris buildup. If your feet sweat really bad when you run, it’s the right environment for a bacterial infection.

Chronic Ingrown Toenails

If you get ingrown toenails regularly, that means that your feet aren’t getting the care that they need, which can lead to infection and/or discoloration. If the toenail changes to black, it could indicate necrosis, meaning death of cells or tissues in the toenail area.

Green Nail Syndrome

More commonly known as green nail syndrome, the proper name is chromonychia. It’s a nail disorder that is characterized by a discolored nail bed, often green/green-black. It is typically a result of chronic paronychia, or infection of the skin around the nail folds.

Subungual Melanoma

We all know that melanoma is the most serious form of skin cancer, and it can grow underneath your nail bed, appearing as a dark brown spot which will make the toenail look discolored even if it’s actually underneath the toenail.

When Do I Need to See a Doctor for Black Toenails?

If there wasn’t an incidence of trauma and your nail is slowly starting to change color, then you probably should see a doctor because it’s not a trauma-induced black toenail. This is especially important if that extension of color goes beyond the nail.

If you know your shoes are too small and you’ve been running a lot or if you’ve been doing a lot of downhill running, you are probably fine to hold off on seeing the doctor to wait until things heal at home.

This should be self-evident, but if the pain is strong within hours of the trauma, there might be a more serious issue going on, so you should see a medical professional. You may also want to do so if you have an underlying condition like diabetes.

How Can I Prevent Black Toenails?

Keep Your Toenails Short

First, it’s important to keep your toenails short, especially if you run regularly. Make sure that there’s a thumb-width distance from the tip of your longest toe to the end of your shoe. This was my downfall.

When I got shoes with more room in the toe box, I haven’t had any issues with black toenails, even though I’ve been running more, including some steep downhill running as well.

Size Up Your Shoes

If you’re a new runner, you might not realize that you really should order half a size up from your typical street shoe. When you purchase your next pair of running shoes, make sure that you get ½ size up because your toes will have more room to breathe.

Pick a Wide Toe Box

Wide toe boxes are useful for other ailments like bunions, but they are also great for avoiding bruised or black toenails. With a wide toe box, your forefoot can rest comfortably in the shoe without getting pinched on the sides.

Wear Thinner Socks

It could be that you have that thumb-width of distance and there’s plenty of room in the toe box, but you just are wearing socks that are too thick. Try wearing thinner socks so that your feet take up less room in the shoe.

My personal favorites are Swiftwick’s PURSUIT Zero Ultralight socks, which just recently launched. They are amazingly comfortable and give you plenty of cushion while still being super light.

Since I live in the South and it’s always very hot in the summer, these socks are my go-to, and I wear them every single day that they are clean. If you need more room in your shoes, you can’t go wrong with them.

Wash and Dry Your Feet and Toes Regularly

Finally, the best way to avoid infections is to make sure that your feet and toes are clean. Thus, it’s important to take the time every day to wash and dry your toes so that there isn’t debris piling up and it isn’t a warm, moist environment ideal for bacterial infections.

How Do I Treat Black Toenails?

While it’s great to know how to black toenails, if you already have them, you’ll want to know how to treat them.

Be Patient

First, if you’re dealing with a trauma-induced black toenail, you’ll need to be patient. In mild cases, the black toenail will simply grow out. And it’s not a fast process, especially if it’s your big toe. Expect six to nine months or longer for the black toenail to grow out.

My experience was that it took around three months for my second toenails to grow out, but close to a year for the big toenail. I did paint my toenails some because they looked so ghastly, but it’s better not to paint them because they need to breathe in order to heal faster.

It is okay if you continue to run with black toenails (otherwise you could be out for a very long time!) as long as there is no pain. If you do feel pain, then running will make the situation worse.

Soak in Warm Water

If your toenails and/or feet feel irritated, soaking them in warm water is sure to do the trick and relieve some of that irritation. This also gives you the opportunity to wash and dry your feet and pamper them a little bit.

Use Cream for a Fungus

If you have a fungus, you’ll want to use an antifungal cream to treat a fungus. You’ll also want to avoid putting your feet in situations where it’s going to be a warm, moist environment to allow the fungal infection to heal and not get worse.

Go to the Doctor

In the case of pain (trauma-induced or not), you’ll want to head to the doctor, who will poke a few holes into the nail to drain the blood. This will also relieve pressure on the toenail and can help save the nail in some cases.

Deal with a Nail Ripping Off

Finally, if you suspect that your nail is getting close to falling off or is getting really ragged, try to keep it trim so that it doesn’t catch on anything. However, if it does rip off and cause injury, you’ll want to first apply pressure until the bleeding stops.

Then apply an antibiotic ointment and cover your toenail with a bandage to prevent infection. Do this every day after showering for about 1-2 weeks. However, if possible, try to avoid this situation!

Final Thoughts

Discolored toenails are never attractive and they are sometimes painful, so it’s important to know not only how to treat black toenails but also how to prevent them! Hopefully, this article has given you a good start in knowing how to take good care of your feet.

The Wired Runner