I started using ivermectin as a prophylactic for about 2 months ago. I didn't take it thinking that it would do anything for my issues with cold sores but after taking ivermectin I noticed how my lips felt different. It was pretty much guaranteed I would get cold sores when my lips would be chapped or I would pick at them and they always felt like there was something under the surface. After taking the ivermectin the feeling is gone and I had severe chapped lips last week and no signs of a cold sore. I can definitely tell a difference at least in regards to the cold sores. I was dealing with the cold sores for about 10 years now.