Zovirax Cold Sore Cream contains aciclovir, an anti-viral, which penetrates deep into the skin to fight the virus which causes cold sores. Zovirax is effective at both the tingle and blister stage, and shortens the duration of pain. Zovirax is clinically proven to help heal cold sores in as little as 3 days*. Use five times a day at approximately four hourly intervals for at least four days. Zovirax Cold Sore Cream helps you get your healthy lips back. Contains aciclovir. Always read the label. (*Median healing time is 4 days. 25% of users healed in 3 days.)