Blisters: What Causes Them?

Blisters form when the skin is in contact with a surface and an attempt is made to move across the skin with an external force.  In response to this, a frictional force will oppose this movement.  As a result of repeated friction a reddened area forms around the rubbing, and this is called a “Hot Spot”. With continued rubbing, the person will feel a sting or burning sensation with a pale narrow area forming around the hot spot.  This pale area then enlarges to encompass the reddened area.  The area is then elevated over the underlying skin as it fills with fluid.

If you have any “hot spots” during activity, it’s important to either cease the activity, or to tend to them right away to prevent or stop further blistering.

Blisters: Influencing Factors

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 cycles necessary to produce a blister.  Higher exercise intensity can increase frictional forces and longer exercise duration results in more shear cycles.  Both increase sweat production and create a moist skin environment.

The most common areas to get blisters are on the soles of feet and palms of hand where skin is thickest. Note that blisters are more likely to form in areas that have thick skin, or callus, because a callus forms for the same reason blisters do, i.e. friction.

Blister Prevention

The best strategy is to adopt a two-pronged approach to reduce frictional influences, namely, the use of a lubricant and the use of socks made from technical fabrics.

Petroleum based lubricant products simply sit on the surface of the skin holding water in the skin and blocking evaporation. This means that extra water is available to flow into any open spaces which form in the skin.  It has been suggested that petroleum based products can actually increase the chance of blistering.

Foot powders are often applied in an effort to minimise blister formation.   These products use talc, or grain starches such as corn starch, as their major ingredient.  Grain starch powders tend to have a greater capacity to absorb moisture than talc based products.  Talc provides good lubrication and protection from discomfort caused by moisture and heat. 

Striderm Anti Blister Foot Powder with Deodorant is talc powder-based product and other technical ingredients including polyethylene, polytetrafluoroethylene, synthetic wax and a zinc complex.  These ingredients work together to repel moisture, reduce friction, and deodorise the feet.  This means that the powder assists in wicking moisture away from the feet while at the same increasing the level of lubricity.

In order to minimise problems, there is an overarching need to look after your feet (and hands, if using trekking poles) in those areas that are prone to blister formation.  This means that it is important to use your anti-blister foot powder every time that you exercise so as to minimise damage to the surface of the skin.