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How Runners Should Treat a Blister Under a Callus

Blisters are an inevitable part of being a runner. We all deal with them at some point, and most runners learn to recognize the signs early and treat them quickly so we can get back to running pain-free.

But what happens when you develop a blister under a callus? This is a bit trickier to treat than a regular blister, but there are ways to relieve the pain.

Here’s what you should know about treating a blister underneath a callus if it happens to you, as well as some ways to stop it from happening again.

What Is a Callus?

A callus is a thickened area of skin that’s usually found on the feet or hands. Calluses happen in high-friction areas as the skin tries to shield itself from rubbing. It’s the body’s way of trying to protect itself from damage.

You often find calluses on the palms of the hands in those who do manual labor or lift weights without gloves. In runners, calluses are often found on the feet in areas subject to a lot of friction, like the heel and underneath the foot.

How Do You Get A Blister Under a Callus?

A blister occurs when there’s friction between the skin and something else. In runners’ cases, friction between your skin and the sock or shoe usually leads to blisters. The friction causes the top layer of skin to separate from the layers beneath it, which causes fluid to build up in the space between layers.

So how does it happen underneath a callus? It’s the same principle—friction happens, and the layer of skin beneath the callus tears away from the layer of skin below it. A blister forms just like it normally would, only with the thick skin of the callus on top of it.

Can I Pop A Blister Under a Callus?

It’s tempting to pop the blister under the callus to provide some relief. While it can release the pressure, there are risks to doing this. Firstly, getting a needle through the thick skin of the callus can be difficult and may do more damage than good.

Secondly, it can be difficult to drain the blister properly. This opens it up to becoming infected, as you can’t keep it clean underneath the callus. If you think a blister under a callus is bad, don’t think about an infected blister under a callus!

How To Treat A Blister Under a Callus

Instead of popping the blister, resist the temptation and treat your blister this way instead. It takes a little longer, but it’s much safer and more effective.

1. Make Sure That’s Really What It Is

You may think it’s easy to diagnose a blister underneath a callus, but it can be easy to confuse it with other skin conditions on the foot. Take a bit of time to make sure you don’t just have inflamed, cracked, or painful skin.

If you can’t tell, it might be worthwhile making an appointment with your doctor to get a proper diagnosis. They may also be able to give you good advice on treating it!

2. Thin Down the Callus

Unlike a regular blister, which you can easily drain and treat, a blister under a callus is blocked by unusually thick skin. If you want to reach the blister to be able to treat it, you need to wear down this layer of callused skin safely.

There are a few different ways you could do this. The skin is so thick that it often doesn’t feel the same way normal skin would. However, you still need to be careful because the pressure on the blister beneath will be painful. You can try to:

  • File the callus down carefully
  • Flake the skin away with a razor blade

Whichever you choose, it’s highly advisable to soak your foot in saltwater or use salicylic acid to soften the skin of the callus before doing either one. You may need to do this for 3 to 4 days before it becomes soft enough. A salicylic plaster is a good idea or an easy-to-apply stick.

Keep in mind that if the callus is extremely thick or painful, you may need to see a podiatrist instead of filing it down yourself.

3. Keep It Clean

You will likely need a few days to file the callus down enough to expose the blister underneath it. During this time, you must keep your foot as clean as possible. Any hint of dirt or sweat could be a gateway to infection.

Keep the newly exposed layers of skin free from bacteria by washing it a few times a day with mild soap and water. Pat it dry with a clean towel, and make sure you’re wearing clean socks.

4. Treat the Blister

Once the callus is filed down enough to expose the blister, you can drain it if you want instant relief. Take note that if it’s a blood blister, you should rather see a doctor to treat it professionally instead of popping it yourself.

But if it’s filled with clear fluid, you can gently pierce the skin with a sterilized needle. It’s a good idea to disinfect the area first and wear gloves because it’s very easy for bacteria to cause an infection at this stage.

5. Cover & Protect It

As soon as you’ve drained the blister, apply a layer of antibacterial cream and plaster or a moleskin patch. This will keep the blister protected and clean until it can heal. Moleskin should help to prevent any more friction on the area.

Depending on how it feels, you could get back to running at this point. But if you feel friction or pain in the area, it may be wise to take a short break until it’s fully healed. Running while you still have pain can lead to you altering your form without even realizing it, which can lead to other foot and joint problems.

How To Prevent A Blister Under a Callus

A blister under a callus is an unpleasant occurrence. The best way to handle it is to prevent it from happening in the first place! Here are some tips.

Re-Evaluate Your Footwear

If your shoes chafe you in one particular spot, you may want to consider changing them. There should be at least a finger’s width of space in between your toes and the front of the shoe, and your toes should be able to spread out without being restricted by the shoe’s upper.

If the toe box is an issue, you may want to choose a pair of shoes with a wider toe box, like Altras, which have a foot-shaped toe box to allow your toes plenty of space. If the ball of your foot is a problem, you should consider a pair of shoes with more cushioning in the forefoot.

You should also ensure that your shoes provide the right support for your feet—stability shoes for overpronators—and that you can lock the heel down so your rearfoot doesn’t move up and down as you run, which will significantly reduce the chance of chafing in the heel.

Choose Moisture-Wicking Socks

If you’re wearing cotton socks, you may inadvertently open yourself up to blisters. Cotton holds onto water, so it’s in your best interest to get rid of them and invest in a few pairs of moisture-wicking socks.

Moisture is a big culprit when it comes to friction and blisters. This is an especially important step if your feet sweat a lot.

File Calluses Down Early

If you notice calluses starting to form, stay on top of them by filing them down before they get too thick. This might not necessarily stop blisters from forming underneath thickened skin, but it will be much easier to treat blisters if the skin isn’t overly thick.

You can use a pumice stone to keep your calluses under control, or you can even get an electric callus filer.

Try to Stick to Flat Terrain

We know you can’t always control the terrain, and it’s also good to train on hills. But if possible, try to train on flat ground as much as possible. This means there’s no excess pressure on your toes or ball of the foot as you’re running downhill, which can contribute to blisters forming.

Ben Drew

Ben Drew

Ben is an avid road and trail runner, and has completed multiple marathons and ultras. A former running store owner, he now shares his knowledge and experience writing these articles.

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