Herpes Simplex Virus (HSV) is a common skin condition that can cause painful blisters on the mouth and/or genitals. There are two types: HSV-1 can cause mouth or genital symptoms. HSV-2 usually causes genital symptoms. Many people with HSV-1 or 2 will never experience symptoms at all. For those who do get symptoms, there is medication to help, but no cure.