Virasolve is formulated to act against cold sores in three ways - it contains an antiviral (idoxuridine) to fight the cold sore virus, it contains an antibacterial (benzalkonium chloride) to prevent infection and an anaesthetic (lignocaine hydrochloride) to relieve pain and itching. If you start treatment with Virasolve as soon as you can feel the cold sore developing you can prevent it becoming visible.