What [Really] Causes Blisters On Feet?

by Rebecca Rushton

You probably think blisters are caused by heat, moisture and friction? I'm afraid that's not really true.

Yes your foot gets hot in your shoe, yes that makes your foot sweat, and yes that moisture increases friction levels. But what causes blisters is... the skin stretching too much.

Watch the video below to see how.

 

Let me tell you a quick story...

One day back in 2008 I was on my morning walk. I was 8 minutes in and I started to get that familiar hot-spot feeling at the back of both heels. I tightened my laces, which relieved things a bit, and kept going. But shortly after that, I felt that familiar stinging pain of a blister.

What the ...

I was confused. 

Not only was I 100% sure my foot wasn’t moving in my shoe, I had taped my heels, like I do every morning. Plus I had been walking for only 8 minutes - my feet weren't that sweaty yet. So where was the heat, moisture and friction coming from. How on earth could anything be rubbing on my skin - it was fully covered with tape!

What causes blisters - is it the shoes?I do my laces up tight to stop blisters - image credit

 

The fact is, there wasn’t anything rubbing my heel. But because of the way my heel bone was moving inside my foot, my skin was stretching up and down with every step I took. And I could feel it! 

When the skin stretches (shears) too far and for too long, the connections between skin cells fatigue and break. These tiny tears under the skin surface are the start of the blister injury. Fluid fills the injured area and within 2 hours, you'll have a blister.

The relevance of heat, moisture and friction.

The popular theory is that heat, moisture and friction cause blisters. While these factors are relevant, they represent a shallow and incomplete understanding of the blister process - and an unhelpful one at that. Here's why:

It gets hot in your shoe (heat) - that's unavoidable. This makes your foot sweat (moisture) - that's unavoidable. This increases friction levels (friction) - that's unavoidable. Try keeping your feet cool and dry in your shoes when you're exercising - it's impossible!

Double meaning

Friction has an unfortunate double meaning: one is rubbing, the other is the force that resists rubbing. The latter definition is the one we need to use. High friction levels cause the skin, sock and shoe to stick together for a bit longer. And because the bones continue to move inside your foot, the skin is made to stretch.

Shear is normal and it happens with every step you take. Thankfully, the feet are able to tolerate a lot of it. Blisters only occur when shear is excessive and repetitive. That threshold is different for everyone ... some people are blister prone, others seem to be blister-resistant.

 

What's next?

With your new-found knowledge of what causes foot blisters, use these resources to get you started on truly successful blister prevention and treatment.

  1. Reduce friction levels
  2. Reduce peak pressures
  3. Reduce bone movement - a podiatrist can help you with this
  4. Alter your skin’s cellular make-up to increase its resistance to blister-causing shear

     





    Rebecca Rushton
    Rebecca Rushton

    Author

    Podiatrist, blister prone ex-hockey player, foot blister thought-leaderauthor and educator. Can’t cook. Loves test cricket.


    Leave a comment


    Also in Blister Blog

    taking blister action sooner rather than later
    Sooner Rather Than Later: Lesson #6 From Adelaide 2019

    by Rebecca Rushton 2 Comments

    At the risk of sounding repetitive, it’s much smarter to take action on blisters sooner rather than later - before they're in a bad state. Here's why and an example of the difference it can make.

    View full article →

    posterior heel edge blisters from orthotics
    When Orthotics Cause Posterior Heel Edge Blisters [And What To Do About It]: Lesson #5 From Adelaide 2019

    by Rebecca Rushton

    Foot orthotics can cause posterior heel edge blisters when they sit ever so slightly out-of-place in the shoe. Find out the easy fix to this problem (you'll need some double-sided tape).

    View full article →

    Using an Engo patch to prevent and treat pinch blisters when wearing toe-socks
    A Solution To Pinch Blisters With Toe-Socks: Lesson #4 From Adelaide 2019

    by Rebecca Rushton 1 Comment

    This article explains a handy alternative to relieving pinch blisters when wearing toe-socks and when space in the shoe's toe-box is limited.

    View full article →