Cold sores are small eruptions usually affecting the lips at the point where the lip joins the skin of the face. They tend to recur in the same place. They begin as a tingling sensation, and then a small blister (vesicle) forms, which then crusts over to leave a small scab that eventually heals.
They are caused by a virus called herpes simplex virus (HSV). It is similar to the virus that causes chickenpox, as are the blisters that result.
