Foot Blisters: What Causes A Blister To Form And When Do You Know?

Blisters form when the skin of the foot is in contact with a stationary surface (e.g., the inside of a shoe) and an attempt is made to move across the skin with an external force (your body’s momentum through your foot strike). In response to this momentum, a frictional force will oppose this movement. With this repeated friction, a reddened area forms around the rubbing, and this is called a "hot spot".

With continued rubbing, an individual will feel a stinging, or burning, sensation with a pale area developing around the hot spot. This pale area then enlarges to encompass the reddened area, which is then elevated over the underlying skin as it fills with fluid. The most common areas for blister formation are the soles of the feet, under and between the toes and around the heels.

What Factors Influence The Degree Of Foot Blister Formation?

The major indicators for blister formation are the magnitude of frictional forces and the number of times an object cycles across the skin. These will determine the probability of blister development: the higher the frictional forces, the fewer the cycles that will be necessary to produce a blister. Higher exercise intensity can increase the frictional forces, while longer exercise duration will result in more shear cycles.  Both the higher exercise activity and longer exercise duration can result in increased sweat production to create a moist skin environment. 

It is worth noting that blisters are more likely to form in areas that have thick skin, or callus, as the callus forms for the same reason as blisters do, i.e., friction on the skin.

Ideally, if you develop any "hot spots", it is important to cease the activity, or to tend to them right away to prevent, or stop, further blistering. Obviously, this is not always practicable, or even desirable, from an individual’s point of view.

What Steps Can Be Taken To Protect The Feet From Blister Formation?

There is a general need for you to look after your feet with a particular focus on those areas that are prone to blister formation. This may mean having regular foot treatments (pedicures), and to apply moisturisers to keep the skin soft. While it may sound counter-intuitive, softer skin provides increased resistance to blisters.

You can take further steps to minimise the risk of blisters by choosing well-fitting socks made from a suitable technical fabric. In addition, the choice of good, well-fitting shoes that are suited to the intended use is also important. If necessary, you should make use of the lace locks, if they are available, to decrease the movement of your feet inside the shoes.

Finally, you can use a lubricant to decrease the friction levels inside the sock and shoe. One common lubrication approach is to use a petroleum, or petrolatum, based product. These products tend to sit on the surface of the skin locking in water and blocking evaporation. This means that extra water is available to flow into any open spaces that form in the skin. It has even been suggested that petroleum based products can increase the chance of blistering.

Silicone and wax-based products, on the other hand, allow the moisture to pass.

What Products Help With Blisters? 

Both Chafe No More and Anti Chafe Extreme are silicone and wax based and can be used to effectively aid and prevent blisters. Simply apply the product to areas likely to blister ie. on the soles of the feet, under and between the toes and around the heel. The products lubricate the area and prevent friction from occurring. You can also apply the chafe no more of anti-chafe extreme directly to the shoe and around the edge of the shoe for an easy and fast transition in a triathlon.


Information used on this site is not intended to diagnose, treat, cure or prevent any disease. If you are concerned about your magnesium levels, please contact your GP. Use only as directed.