For those who are predisposed to cold sores/fever blisters. You may notice that just prior to the eruption of the blisters, you get a tingling, sometimes itchy sensation, even when there is no sign of an impending outbreak of blisters. At this point, place ice directly on the area and hold it in place for at least 20 to 30 minutes. This is very effective at heading off an outbreak. I read this in Lancet a few years ago and it really does work.