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What Causes Black Toenails
from Running?

Black toenails from running are caused by the toes continuously hitting the front of the shoe while running. The constant hitting causes a blister to form under the nail which pushes the nail away from the nail bed. Blood gathering in the blister causes the nail to appear black.

There are a number of reasons why this happens. Feet swell when running reducing the space they need inside the shoe. Many runners are wearing shoes that are not big enough to allow for the extra space needed. 

An increase in downhill running can cause your feet to slide forward more than they would normally. In hot weather, your feet will sweat more and slide forward more inside the shoe. Runners often develop black toenails following a race. This is a result of the increased pace they are running during the race and increasing the force of impact of the toes against the shoes.

How can you Prevent Black
Toenails from Running?

Because feet swell when running, running shoes need to allow extra room for the swelling. Your running shoes should have a wide toe box and should be at least one half size larger than your regular shoes. Keep your toenails well trimmed to protect your nails and to prevent black toenails when running. 

During a long run, keep your feel dry as long as possible to reduce sliding inside the shoe. Use moisture wicking socks to help. Tying your shoe laces tighter along the front may help keep your feet from sliding forward. If black toenails from running continue to be a problem for you, you may want to try protective toe caps.

What to do if you Develop Black Toenails from Running?

You really don't need to do anything if you have a black toenail from running. If your toe is not too painful and you don't mind losing the nail, then it is not usually a problem. Just let the nail grow out and fall off. Another one will grow back to replace it.

However, if you see any sign of infection or if it is very painful and the pain does not go away, you need to see a doctor. It will take about three months for the nail to fall off.

There are many runners who treat this condition safely at home. If you are in a lot of pain or you want to try to save your nail, you can try the following treatment at home. However, it needs to be done as soon as possible. If you wait 24 hours, the blood will have started to dry and you won't be able to drain it. 

Black Toenails from Running

If the blood blister is near the end of the nail, you can use a hot needle (heated over a flame) to break the blister. Press on the blister to remove as much blood and liquid as possible. This will help relieve the pain and pressure. Apply antibiotic cream to the blister area to prevent infection. 

If the black area is in the center of the nail, you will need to make a small hole in the nail to drain it. Use a paper clip that has been heated over a flame. Push the red-hot paper clip through the black part of the nail to create a small hole for the blood to drain. Press on the nail to remove as much liquid as possible. Then apply antibiotic cream on and into the bruised area. This doesn't usually hurt although it sounds quite painful. 

Again, if the pain doesn't go away or there are signs of infection, see your doctor.

For the vain among us who do not want to attempt to drain the blood but want to cover up the black nail, there are various shades of nail polish that can cover black toenails quite well. Popular colours to use are: dark purple, deep burgundy, metallic silver, or use a black polish with colorful flowers.

Then there are those among us who proudly display their well deserved badges of honor without shame -- and bravo for you! Most runners have experienced or will experience black toenails from running at some point in their running career and it is really a personal choice how to deal with them.  

Your black toenail story

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