Why Runners’ Toenails Fall Off + 4 Helpful Tips To Prevent It

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There are lots of wonderful things that running can do for your body. To name a few, your muscles become stronger and more defined, your heart becomes more efficient, and your body composition improves.

However, running is also hard on your body, and the repetitive nature and impact of your foot hitting the ground stride after stride, mile after mile, can also cause a few undesirable changes.

For example, some runners deal with chafing, the painful rubbing of skin against skin or fabric against skin, and some even experience runner’s face, a seeming premature aging of the facial skin.

Another common trouble spot is the toenails. Many runners complain of losing toenails from running or having black and blue toenails. Most also wonder why runners’ toenails fall off.

In this article, we will discuss why runners’ toenails fall off, the reason why you might be losing toenails from running, and how to prevent your toenails falling off from running.

Black and blue toenails.

Why Runners’ Toenails Fall Off

Although a toenail falling off from running is not uncommon and is sometimes even considered a badge of honor among certain runners, it can be painful and, if not managed well, can even increase the risk of infection.

The primary reason why runners’ toenails fall off is that a subungual hematoma develops under the nail.

This refers to bleeding underneath your toenail and will visually result in blue, bruised, or black toenails from running.

In fact, black toenails from running are so common that the condition has earned the recognized name “runner’s toenail” or “runner’s toe.”

The discoloration associated with runner’s toe is due to blood trapped under the toenail that has leaked out from broken blood vessels.

Essentially, runner’s toenail (subungual hematoma) is a bruise (hematoma) under the toenail (subungual).

Runner’s toenail or toenails falling off after running is usually because of the accumulated microtraumas your toe experiences during the gait cycle rather than resulting from one acute misstep while you run.

A black toenail that will likely fall off.

In other words, black toenails from running are due to the repeated stress of your toenails ramming into the front or top of your shoe rather than a sudden, sharp kick where your foot hits a rock, root, or curb.

Typically, the toenails that fall off from running are those found on your longest toes, usually the big toe or second toe, because these are the toes that take the brunt of the impact every time your foot rams into the inside of the shoe.

This can occur at ground contact when your foot first lands during each stride as well as during push-off when your toenails might rub against the front or top of your shoe if the shoe is either too tight or too loose, either constricting or allowing too much motion of the foot inside the shoe.

Because you take thousands of steps per run, these little microtraumas accumulate and can damage the blood vessels under the toenail that supply the nutrients the toenails need to survive.

Initially, this damage results in bleeding underneath the nail, which will appear as purple, blue, or black toenails from running. However, if the damage prevents the nail from receiving adequate blood flow and nutrition, the toenail can eventually fall off and die.

This is why toenails falling off from running is quite a common malady amongst distance runners.

A person holding a bruised toenail, a cause of why runners' toenails fall off.

Other Causes of a Toenail Falling Off From Running

In addition to runner’s toenail and losing toenails from running, there are other potential toenail injuries from running that may or may not lead to your toenail actually falling off but can still affect the appearance and comfort of your toes in, under, and around your toenails.

A separate but similar issue to a subungual hematoma or runner’s toenail is a blood blister under your toenail from running. 

Blood blisters under your toenails usually occur due to repetitive friction over damp or sensitive skin. 

Most commonly, this occurs when the toenail is subjected to shearing forces back and forth against the top inner surface of the shoe as you run due to poorly fitting shoes or socks that are too thin.

According to the Cleveland Clinic, getting a blood blister under your toenail can lift up the toenail, which may cause the nail to eventually fall off.

Blisters under your toenails or on top of your toenails may also be filled with clear fluid, or plasma, rather than blood, but regular blisters can still be painful and may still cause your toenail to fall off if the blister fills with enough fluid and lifts the nail too far up away from the nail bed.

A person with fungus on their nails.

Other Toenail Issues In Runners

Another common toenail issue in runners is fungal toenail or fungal infections of the toenail.  According to the Mayo Clinic, toenail fungus, also called onychomycosis, is caused by the same fungus associated with athlete’s foot (tinea pedis). 

Fungus can grow in warm, damp environments like inside sweaty running socks. Fungal infections in the toenails result in toenails that may be thickened, yellow, brittle, and smelly. 

How to Prevent Your Toenails Falling Off From Running

As can be seen, there are several common toenail issues in runners. There are some preemptive toenail and foot care strategies that can help prevent these issues.

#1: Trim Your Toenails

When your toenails are too long, they jut out past your toe, leaving them in a vulnerable position to collide with the front inside of the shoe. 

Regularly trimming your toenails so that they stay neat and short can prevent them from extending beyond the length of your toe, potentially preventing the microtraumas that result in runner’s toe.

To minimize the risk of ingrown toenails, clip your toenails straight across rather than along a curve.

A person getting their toenails clipped.

#2: Wear Running Shoes That Fit Properly

Wearing running shoes that are too small/short or too narrow in the toe box or do not have enough height in the toe box around your feet can cause your toenails to ram into the ends of your shoes as you run. 

On the opposite end of the spectrum, wearing running shoes that are too big allows your foot to slide around, which can lead to blisters from friction or runner’s toenail from your toes sliding into the front of your shoe, especially when you run downhill.

The running shoe should have about a thumbnail’s width between the end of your toes and the shoe in terms of length. Regarding the proper width and volume, you should be able to freely wiggle your toes without them bumping into the sides or top of the shoe.

Additionally, when it comes to getting the proper fit with running shoes, it’s also important that the shape and width of the shoe adequately fit your foot, not just the overall size.

The shape of the shoe should mimic the shape of your foot. For example, some running shoes have a more tapered toe box that comes to a point, whereas others are more squared off and broad.

If the shoe is squishing your toes together, your toenails are more likely to rub against the sides or front of the shoe, which can cause blisters or bruised toenails.

A running sock.

#3: Wear Running Socks

Runners focus a lot on their running shoes in terms of preventing toenails from falling off from running, but wearing the right socks is nearly as important for the health of your toenails. 

Cushioned running socks with a seamless toe can help absorb force and shield your toenails from ramming into the end of the shoe. 

The right socks can also prevent blood blisters under your toenails and blisters forming at the tips of your toes because the sock can prevent shearing and friction of the toenail and toe skin from rubbing on the shoe.

Running socks should also be moisture-wicking to help prevent fungal growth. As soon as your run is over, take off your damp socks and either shower or wash off and dry your feet to deter fungal growth.

For help on how to choose the perfect running socks, click here.

A person lacing up their running shoes.

#4: Use Your Laces

You can play around with different shoe lacing patterns to customize the fit of your running shoes and prevent excessive sliding of your foot inside the running shoe. 

If your toenails continue to bother you from running, speak with your doctor or podiatrist for further evaluation and guidance. 

You may need to try out a variety of different running shoe lacing patterns before you find the one that works for you.

For instructions on how to lace your running shoes and pattern ideas, check out the following guide:

How To Lace Your Running Shoes: 4 Different Options To Try Out.

A person lacing up their running shoes.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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