Treating a blister is straightforward. Blisters are usually caused by shoes rubbing or something being to close to the skin causing friction. When a blister appears you maybe tempted to pierce it, but don’t. The liquid that is found inside a blister is called serum, it your skins natural healer and it helps with the healing process. Cover the blister with a plaster or special blister plaster and in a few days the blister should have gone down.