A blister is a raised piece of skin that is most often filled with clear fluid. Sometimes blisters are filled with blood (blood blisters) or pus caused by an infection. While they can form anywhere on the body, they are most commonly found on the feet and hands.
Blisters are caused by excessive rubbing of the skin and are most likely to be found on places of the body that sweat the most. Blisters can often be red, itchy, and painful. Many blisters can be diagnosed and treated at home, you should see a doctor if you have an infected blister, recurring blisters, blisters in unusual places (other than the hands and feet), blisters that result from a sunburn, burn or scald.