Virasorb cold sore cream contains the active ingredient aciclovir, which is an antiviral medicine used to treat infections with the herpes virus. This cream is used to treat cold sores, which are caused by infection with the herpes simplex virus. Aciclovir works by stopping the herpes simplex virus from reproducing and infecting more cells.
Aciclovir is converted to a more active form inside cells of the body that are infected with herpes simplex. The activated aciclovir works by blocking the action of a viral enzyme called DNA polymerase.
The cream is most effective if treatment is started as soon as the first signs of a cold sore (a tingling sensation), begin to appear, though treatment can also be started after the cold sore blister has appeared.