Everything You Need to Know About Runner’s Toenail

If you've ever noticed that your toenail hurts when you press on it after a long run, you may have a sore toenail from running. When one or more toenails hurt, the throbbing sensation can make running, and even walking, pretty uncomfortable.

In many cases, a sore toenail is the first sign of developing runner's toenail, also known as black toenail. Fortunately, there are a few steps runners can take to avoid sore toenails and prevent black toenails. If you already have a sore toenail, find out what you can do so you can get back to running without the pain.

What Is Runner’s Toenail?

At the end of a long walk or run, you may notice that a toenail has turned black, blue, or gray, and your toe may be swollen under the nail. These black toenails are due to bleeding under your nail, which is also known as a subungual hematoma.

But you don't have to wait that long to start running again. Once the black toenail falls off, the nail bed is typically less tender. In some cases, a new nail may already be starting to grow underneath the black toenail, which may speed up your recovery time. Many runners will keep running while they have a black toenail if it isn't causing them too much pain.

Risk Factors for Runner's Toenail

Anything that contributes to repeated trauma to the toenail area is a risk factor for developing a black toenail. Whether you're running or walking, hilly terrain (especially downhill) can cause the toenail to press repeatedly against the front of your shoes. The longer the exposure, the higher the risk. So packing on the miles quickly can lead to enough trauma to develop a subungual hematoma. Ill-fitting shoes are also a risk factor.

What Causes Runners to Get Black Toenails?

As you walk or run, your foot slides forward in your shoe, banging your toes against the top, front, and sides with each step. Additionally, it's common for your feet to swell during a walk or run and get compressed by your socks and shoes. That pressure and impact can cause toenail soreness, damage to your toenail beds, or a blister to form under the toenail itself.

When this happens, the extra blood and fluid cause your toenail to separate from the nail bed. The blood colors the toenail black. Your toenail will probably continue to change colors during the course of healing.

Other Non-Running Causes

There are reasons apart from running that a toenail can change color. It's important to be aware of these other conditions so that you can address the underlying cause of toenail discoloration.

• Injury or trauma: Sustaining an injury to a toenail can cause it to turn black. From stubbing your toe to dropping something heavy on it, injury can cause blood to pool, resulting in a black toenail. This will usually heal on its own, but if you suspect damage to more than just the toenail from an injury, seek advice from a healthcare professional.
• Fungus: Fungal infections of the toenail can also cause color changes in the nail, from gray to blue, brown, or black. If your black toenail didn't appear suddenly after a workout or after dropping something on your toe, fungus may be to blame. Over-the-counter antifungal treatments are available, but see a healthcare professional if these are not effective after a few weeks.
• Cancer: Another possible, but rare cause of black toenail is malignant subungual melanoma. Unlike trauma to your toenail, this type of black toenail does not appear suddenly. Instead, you will see a black line or band extending up the nail from the cuticle. One difference between this type of cancer and common toenail trauma is that the black line extends into the cuticle. See a healthcare provider immediately if you are concerned that your black toenail may be something more serious.

Symptoms and Complications

When runner's toe first presents, it can be swollen and the toenail may hurt when you press on it. Minor cases of a black toenail will simply grow out, and you will be able to trim it away.

If the toenail is raised, however, it is likely you will lose the nail. While this can be distressing, it happens to many runners. The toenail should fully grow back, usually within several months to a year.

If pretty, polished toes are important to you, you can paint the black toenail, the new thin toenail, or the bare skin. Most people won't notice the difference if you use a darker shade of polish. Podiatrists can even craft a prosthetic toenail that can last many weeks, though it would be as prone to running damage as a regular nail.

How to Treat It

When you experience sore toenails after running, you will want to give them a chance to heal for a few days. You should only return to running if your toenail pain has subsided. During the recovery phase, you may want to wear open-toed shoes until they are no longer tender to help avoid any further trauma.

Draining a Black Toenail

There is no need to have a black toenail drained if it isn't raised and painful. If swelling and pain persist, a healthcare provider can relieve the pressure by poking a hole in the nail and draining the fluid behind it, a procedure called trephination.

Take infection seriously. If your toe continues to hurt or the pain increases, or if you notice pus or a foul smell, check in with a healthcare professional. Toe infections can lead to blood infections, gangrene, and worse, especially for those with diabetes.

How to Prevent Runner’s Toe 

Prevention of runner's toe comes down to footwear, foot hygiene, and run planning. Your running or walking shoes and socks must fit correctly. Toenails must be trimmed and filed correctly. You should also plan your route and mileage wisely. When it comes to footwear, consider trying a pair of cushioned running shoes.

Check Your Shoe Fit

The first step to preventing sore toenails after running is to check the fit of your shoes. If you're wondering if your current running shoes are the correct size, check the location of your big toe. If it's pushed right up against the front of the shoe, they're too small. You might consider getting wide toe box shoes if you have wide feet.

Another easy way to check the fit is to remove the shoe's insert and stand on it. If any part of your toes is hanging over the end of the insert, your running shoes are too small.

Invest in New Shoes

If you suspect that your shoes don't fit correctly, invest in a new pair. When shopping for running shoes, make sure you go to a specialty running store and have the salesperson measure your feet.

When trying on shoes, try several different pairs. Most new shoes feel great when you first try them on. If any part of the shoe feels weird on your foot or rubs a strange way, think about how bad it could feel after 10 miles. It's best to try on new running shoes after a long run or at the end of the day when your feet are already swollen.

Tie Your Shoes Differently

You can also learn to lace your shoes to retain your heel in the heel cup and prevent your feet from sliding forward in the shoe with each step. Use a simple lacing technique such as the following to prevent heel slippage:

1. Lace your shoe to the next-to-last eyelet.
2. Lace over and down through the top eyelet on the same side to form a "bunny ear."
3. Do the same for the other side.
4. Pull the lace through the opposite "bunny ear."
5. Tie your bow.

This lacing technique will pull the top of the lacing tight at the ankle while keeping the rest of the lacing properly tensioned.

Keeping your foot from sliding forward is especially important for running routes that include downhill sections. You should stop and ensure your shoes are laced correctly before any significant downhills.

Choose Thicker Socks

If your shoes have a sloppy fit, you can wear thicker running socks. Look for versions that have more padding. Keep in mind that cushioning is generally a good idea only if there is room for it in your shoes. If thick socks make your shoes too snug, there’s still a risk of developing sore toenails.

Trim and File Toenails

Toenail length is a major factor in the development of runner's toe. Properly trimming your toenails and filing the edges will make them less likely to hit the inside of your shoes, which can help prevent soreness and bruising. When your toenails are too long, they can start to generate friction and cause irritation.

Switch Up Your Running Routes

Running downhill can be a major contributor to the conditions that lead to runner's toe. While your toenail is healing, find new routes that minimize particularly long or steep stretches of downhill terrain.

Increase Your Mileage Slowly

Adjusting your mileage too quickly is another contributor to the development of black toenails. Suddenly experiencing a greater frequency of toe trauma puts you at greater risk of runner's toe. The same is true whether you are starting a brand-new running routine or you are beginning training for a longer-distance race. Ease off the mileage slightly, then ramp it up a little more gradually.

A Word From Verywell

Don't despair that your fitness activities are hurting your toes. It is likely just a signal that you need to be more careful in selecting your running shoes and lacing them correctly. You might change your mindset and know that a healthy body is better than pretty toes. But with attention to your footwear and a few other preventative measures, you should be able to have both.