What is Herpilyn and how does it work? ## Herpilyn is an over the counter product that is listed as an enzymatic therapy, which they claim can less the severity of cold sores and fever blisters. However, as such a product, it is not actually scientifically, nor medically proven to help with anything. They don't list all of their ingredients, but from what they do list, such as camphor and lemon balm, it is very similar to other products you can purchase, such as Blistex.