Most blisters form when your skin rubs against your shoes or socks repeatedly over time. The damaged upper layer of skin shears away from the layers beneath and fluid collects in the space to create a firm bubble under the skin – forming the dreaded blister. They develop very quickly, can take several days to heal, and if they break open they can become infected, making the pain even worse.
Blisters develop most frequently in the summer because on hot, humid days our feet tend to swell up from water retention, causing our shoes to squeeze our feet in certain areas. Feet also get sweatier in the summer. So, when your feet are both swollen and sweaty it’s a dangerous combination, ripe for feet friction.