Find out more about why the skin on your feet is different here.
Blisters created by friction can can create a separation or rupture between the layers of your skin. This rupture forms a pocket that quickly fills with liquid to give the blister its bubble-like appearance.
They are are a relatively common complaint and the presence of excess mechanical force on the skin is considered the trigger for the development of blisters. When skin is in contact with an object e.g. a shoe or a sock, an external shear force may attempt to move the shoe or sock across the skin.
Shear forces are forces that are applied at sideways angles to the tissue surface. A frictional force will then oppose the movement. Friction is the force between two surfaces rubbing together. When excess shear forces are applied to the skin, movement occurs.
How your skin reacts to friction and shearing forces can depend on the duration and intensity. High forces over a relatively short period of time are likely to result in a blister, whereas lower forces over a prolonged period will result in thickening of your skin and you may develop a corn or callus. Read more about the development of corns and calluses here.