A Comparative Study of the Efficacy of Penciclovir 10mg/g (1%) Cream in Preventing the Appearance of Classical Lesion in Recurrent Cold Sore Sufferers

Inclusion Criteria: * Be known to be a cold sore sufferer and presenting a prodromal stage with pain * Sign the written informed consent form prior to enrolment in the trial; * Be aged 18 to 75 years; Exclusion Criteria: * If female, are pregnant, planning pregnancy or lactating; * Have a known hypersensitivity to penciclovir or any ingredients of the vehicle; * Have already ongoing classical cold sore lesions at the baseline visit; * Have taken any cold sore product, analgesic or NSAID in the 24 hours before the baseline visit; * Have applied a cosmetic lip balm on their lips in the 12 hours before the baseline thermographic assessment; * Are known to be immunosuppressed (acquired, congenital or therapeutic); * Have been involved in any investigational protocol within the 30 days prior to the trial; * Have evidence or history of drug or alcohol abuse;