Ugh, I hate fever blisters! What has worked for me is this. Usually when I'm starting to get one I feel a little tingling and itching around the spot (mine are always in the same spot). Once I feel that I take a few Lysine tablets (over the counter vitamin). That usually stops it from coming on through. I know some people take this vitamin daily as to keep the blisters away but I don't get them that often so just taking a few when they're starting to pop up works for me. If I don't get it in time and it pops up anyway then I take prescription Valtrex. I've tried abreva but it didn't work for me. Hope this helps.