Cold sores, also called herpes or fever blisters, are groups of small, fluid-filled blisters. The blisters are most often gathered in patches on the lip and around the mouth. Before an outbreak, you often feel a tingling sensation or stinging pain. Then the blisters appear, and they usually burst, ooze, crust over and disappear after several days to two weeks. If you don’t treat your cold sore, it usually lasts 7-10 days, but can remain for up to two weeks. Although there is no cure for cold sores, you can control the pain, the severity of the outbreak and you can help speed up the healing process.