Blisters on the feet are caused by rubbing or friction when walking long distances in tight shoes. Blisters can be filled with a clear fluid, blood or pus.
It is important not to pop the blisters as they can get infected. The best course of action is to let them dry out. If the blisters are causing excessive pain, it is best to see a podiatrist to get them drained with sterile equipment, then cleaned and antibacterial chemicals applied.
It is then important to look at prevention methods such as protective dressings, powders and appropriate shoewear.