A blister is an area of raised skin where fluids have accumulated caused by excess friction. A blister begins with a hot spot noted by a sharp, burning sensation. A superficial blister will be filled with clear fluids and a deeper blister can fill with blood if a vessel is ruptured. To reduce the amount of friction and prevent blisters it is important to keep socks dry and wear the correct shoe size. To prevent a blister from becoming more severe, cover the area with friction-reducing materials such as donuts, moleskin, Aquaheal, or second skin. If a blister is still intact and in an area that will receive a lot of friction, the blister may be popped. After the blister has been popped, treat as an open wound and then place a doughnut pad around the area to prevent further irritation.