herpes simplex
"Started to feel the tingle and put some abreva on. Within 2 hours I had 3 small visible blisters. Continued to treat with abreva hoping that it would make it stop growing but it soon grew to nearly half of my lower lip with 8 separate sores. I'm very swollen and have never experienced this degree of cold sore discomfort before. Switching back to my expensive prescription meds, as abreva did not work for me."