{"id":1847,"date":"2023-03-07T13:54:54","date_gmt":"2023-03-07T02:54:54","guid":{"rendered":"https:\/\/pro.blister-prevention.com\/?p=1847"},"modified":"2023-05-20T14:21:00","modified_gmt":"2023-05-20T04:21:00","slug":"what-causes-foot-blisters","status":"publish","type":"post","link":"https:\/\/pro.blister-prevention.com\/blog\/what-causes-foot-blisters\/","title":{"rendered":"What Causes Blisters On Feet: A New Blister Paradigm"},"content":{"rendered":"\n
Updated 2023: Most of us understand that foot blisters result from some combination of heat, moisture, and friction. While all three factors are relevant, this generalisation grossly over-simplifies the actual process. In fact, the perception one is left with is an inaccurate one. It should come as no surprise then that without an adequate understanding of what causes blisters on feet, obstacles to effective management are almost inevitable.<\/p>\n\n\n\n
Try keeping your feet cool and dry in your shoes when you\u2019re exercising even on a cool day \u2013 it\u2019s impossible! But that doesn\u2019t mean you have to get blisters \u2013 even if it\u2019s really hot and humid, even if you\u2019re on your feet all day, even if you\u2019re really sweaty.<\/p>\n\n\n\n
This article highlights the holes in the old heat-moisture-friction blister paradigm and offers a new paradigm for what causes blisters. One that is accurate, easy for the lay population to understand, repeatable and points us towards the array of opportunities for effective management practices.<\/p>\n\n\n\n
Heat is relevant to blister formation. While friction blisters are not a thermal burn,1\u20139<\/sup> we know it is easier to get blisters in hot conditions compared to cold,5,10<\/sup> that there is an increase in skin temperature preceding blister formation,8<\/sup> and there is a prolonged increase in temperature after the blister forms.8<\/sup> What’s more, higher temperatures cause more perspiration3<\/sup> and unsurprisingly, faster walking speeds increase in-shoe temperatures11,12<\/sup> and increased sweating.13<\/sup> This perspiration that provides the \u2018moist\u2019 environment known to increase friction levels 2,14\u201316<\/sup> and blister formation.3,17<\/sup><\/p>\n\n\n\n Friction is a fundamental factor to the cause of foot blisters, but is more counterintuitive than one might expect. Why? Because friction has two meanings. It means both rubbing, and the resistance to movement of one surface over another18<\/sup> \u2013 two contradictory definitions.<\/p>\n\n\n\n In the case of foot blisters, it\u2019s the first definition that the majority of us see in our mind\u2019s eye when we think heat-moisture-friction. However, it\u2019s the second definition of friction that we should be thinking of \u2013 the resistance to movement. The second definition means things rub less \u2013 there is more resistance to rubbing so it takes longer for movement to occur.<\/p>\n\n\n\n So, let\u2019s examine both a low friction scenario and a high friction scenario and determine their relevance to the cause of foot blisters.<\/p>\n\n\n\n Let’s take the greasy lubricant, Vaseline. It is often used on the feet to prevent blisters. Vaseline reduces the skin’s resistance to movement. It makes things more slippery. It reduces the coefficient of friction (COF). Vaseline reduces the friction level and allows things to slip\/slide\/rub\/move across one another more easily. A low friction scenario is one where there is less resistance to movement so that things rub more. This is how lubricants (and other friction-reducing strategies) prevent blisters. Rubbing does not cause foot blisters. In fact, promoting rubbing by way of reduced friction levels is how you can prevent blisters.<\/p>\n\n\n\n High friction levels make things stick together for longer \u2013 an increased resistance to movement. For example, perspiration causes the skin to become clammy or tacky or sticky. It increases the COF. Sweaty feet increase friction levels and make it more difficult for things to slip or slide or rub or move across one another. If movement does happen, it happens much later. This is the increased friction levels that are unequivocally linked to the cause of blisters on feet.<\/p>\n\n\n\n But how, exactly?<\/p>\n\n\n\n It has to do with soft tissue shear distortions (shear deformation). Higher friction levels make the skin, sock and shoe surfaces remain in stationary contact for longer, while the bones move back and forth within the foot as part of normal function. This results in larger shear distortions of all the soft tissues in between skin surface (not moving) and bone (moving). As the bones continue to move within the foot with each step, the skin does not immediately follow. And so the soft tissues in between undergo shear deformation. Picture the individual layers of skin and soft tissue gliding parallel over one another to allow for this skin-bone mismatch. The longer the skin remains stationary, the higher the shear distortion. These shear distortions, when repetitive, are known to cause blisters.1-4, 8,14,16,19\u201324<\/sup><\/p>\n\n\nThe contradictory definitions of friction is responsible!<\/h2>\n\n\n\n
Low friction scenario:<\/h3>\n\n\n\n
Soft tissue shear distortions cause foot blisters via a mechanical fatigue<\/h2>\n\n\n\n