Aciclovir Viraban 5% Cream 5gViraban Cold Sore Cream is an antiviral used to treat & prevent the symptoms of cold sores. (herpes simplex). Antiviral active ingredient Aciclovir, works by stopping the herpes virus from reproducing & infecting other cells. Often you will feel a tingling, itching, burning sensation. Use at the tingle stage. Viraban can prevent the cold sore from developing. If the blister does develop, Viraban can speed the healing process.