herpes simplex
"Abreva used to work for me very well, but it no longer does. I used to put it on and it would shorten healing time significantly, and if I caught it early enough would go away before blistering. The last couple of times I caught one right away and put it on at the first tiny tingle. It still spread to a huge multi-blister sore and took 2 weeks to heal. Either my body has grown resistant to the active ingredient in Abreva that used to work, or they have changed their formula. Very disappointed."