Fenistil Cold Sore Cream is for the treatment of cold sores (herpes labialis). A cold sore is caused by a viral infection. The virus can remain inactive for extended periods of time, but when triggered the virus multiplies and a cold sore develops. This can occur, for example when you are run-down, when you have a cold or flu, or when you have been out in strong sunlight. The virus causes painful blistering of the lips.
