what causes sores with blisters
Both cold sore and fever blister refer to the lip blisters caused by infections of the Herpes Simplex I virus (not to be confused with Herpes Simplex II, which is generally associated with genital herpes). Cold Sores are viral infections which cause recurrent groups of irritating, even painful blisters on the lips. The Herpes Simplex I virus affects more than half of the adult population, and over 50 million people in the US experience at least one cold sore outbreak per year.