Does running barefoot put me at risk of toenail fungus?

Hi My Running Doc!

I have heard that going barefoot in locker rooms can put me at risk of a fungal infection and toenail fungus. Does running barefoot also put me more at risk of a toenail fungus infection? 

Thanks!

Jimmy, San Francisco, CA

Hi Jimmy, 

Great question!  The short answer is no... running barefoot does not actually put you more at risk of getting a toenail fungus infection than running in running shoes.

But before we explain that, let's explain why there is such a high risk of getting a fungal infection from a gym locker room.  People work out at the gym all day long. Most of them shower once they are done. 

So the floors in the locker rooms are continually coated with water dripping off of freshly showered athletes. This leaves the floors in the gym locker rooms perpetually moist. This moisture creates the perfect environment for fungal growth. If you walk around in there barefoot the chances are good you might pick up a fungal infection in the form of athlete's foot.

The same organism that causes athlete's foot is also the same organism that causes fungal toenail infections.

In order to get a toe nail fungus infection you must have a couple of conditions present at the same time.

1. Active fungus and/or fungal spores.

2. Trauma to the toenails.

Much like a gymnasium locker room, running shoes are actually the perfect incubators for toenail fungus. Your feet are like little heaters warming up the inside of the shoes to the perfect temperature for fungal growth.  When you exercise, your feet sweat. The inside of the running shoes are also dark and devoid of sunlight. All of this creates the perfect environment for toenail fungus to grow.  

When you run, the ends of your toes and hence the toenails can bump up against the inside of the shoes. Many marathon runners have witnessed this first hand in the form of black and blue toenails after a long run. It's not a large amount of trauma, just a small amount of repetitive trauma that can cause bruising under the toenail.

If you have this sort of trauma to the toenails when you have foot fungus growing inside your running shoes, the fungal spores and live fungus can get underneath the toenail and start to grow. The result is a  fungal toenail infection.

You know you have thick yellowing discolored toenails indicative a  toenail fungus infection.

When you run barefoot you're unlikely to have trauma to the toenails in the presence of a large amount of toenail fungus or fungal spores that are often coating the inside of running shoes. And in this respect, you're actually a lower risk of getting a toenail fungus infection when running barefoot as compared to when running in heavily used running shoes.

Dr. Christopher Segler, DPM is a marathon runner and 11-time Ironman triathlon finisher.  His podiatry sports medicine practice focuses on convenient rapid treatment of running injuries. He is often invited to speak at medical conferences on the topic of barefoot running biomechanics. You can learn more about running related toenail infections and laser treatment of toenail fungus at www.LaserToenailSanFrancisco.com   If you have a question about a toenail fungus infection or barefoot running injury you can call him directly at 415-308-0833. 

Is this black toenail fungus or a bruised toenail from running?

I have been training for a trail run and have been running on lots of hills in Marin. I recently noticed that I was getting some dark black discoloration of my toenail. I am worried that this might be black toenail fungus infecting the toenail. How can I tell whether the toe is bruised or if I really have a toenail fungus infection? Also, what if anything should I do to treat the black toenail if it is infected?

Thanks,
David, Mill Valley, CA


Black toenails are likely one of the most common injuries I see in runners in Houston and San Francisco. There can be a couple of causes of black toenails from running.

Differences between a bruised toenail and a fungal toenail:
A bruised toenail hurts because 1) there is bruise 2) there is blood under the toenail increasing pressure between the toenail and underlying nail bed. This causes pain in the toenail when you press on it or bump the toenail on the inside of your shoes. Fungal toenails are not usually tender unless the toenail infection has been present long enough to make the fungal nail really thick.  The increased thickness can cause some tenderness, but it doesn't happen quickly.

A bruise comes on quickly, but a toenail fungus infection appears gradually. Bruising will appear within a day or two of your long run, race or whatever injury to the toenail. If you kick a coffee table once with your toe, the toenail may develop a bruise and turn black. If you bump the toe inside your running shoe repeatedly while running down hill (or because the running shoes are too tight) you can also get a bruised black toenail from the cumulative trauma. This can happen overnight.  You wake up and the toenail is black.

The changes in the toenail caused by toenail fungus happen very slowly. The color of the toenail will not change quickly.  The increased thickness, yellow discoloration, white crumbly appearance and dark color of a fungal toenail infection happens so slowly that it is almost hard to notice.

You can learn more about black toenails and toenail fungus treatment here by reading about an example of a black toenail in Houston that actually is just a toenail bruise. You can also read about from runners, blisters and black toenails here.  Learn how a bruised toenail can lead to a toenail fungus infection.

Dr. Christopher Segler, Doctor of Podiatric Medicine is Board Certified, American Board of Podiatric Medicine. He is a 10-time Ironman finisher and marathon runner. He lectures frequently to other podiatrist and foot specialists at medical conferences on the treatment of complicated running injuries and running biomechanics. He is licensed to practice podiatry in Texas, California, and Hawaii. He travels back and forth between Houston and San Francisco to see injured runners who have running injuries that need the fastest treatment based on a runner's goals and running doc perspective. If you live in San Francisco or Marin and have a running injury question call 415-308-0833 to speak to him. If you are in Houston and have a question about a running injury, call him directly at 713-489-7674.