Need to drain a painful blister? To avoid infection, follow these steps: Wash your hands and the blister with soap and warm water. Swab the blister with iodine, and sterilize a clean, sharp needle by wiping it with rubbing alcohol. Puncture the blister at several spots along the edge. Let the fluid drain, but leave the overlying skin in place. Apply an ointment such as petroleum jelly and cover the area with a bandage. After several days, remove the dead skin with sterilized tweezers and scissors. Apply more ointment and a bandage.