What is the duration of a cold sore or a lip blister?

5-14 days: Cold sores can take 5-14 days to fully heal. Taking Valtrex (valacyclovir) (antiviral medication) can reduce the duration of cold sores if taken within the first couple of days from when they erupt.

About 2 weeks: Cold sores result from a re-activation of the herpes simplex virus-a common virus in up to 95% of the population. The lesion undergoes a series of changes over 14 days. Infected patients can infect others whether there is an active lesion or not. Anti-viral drugs based on Acyclovir are available by prescription and can be taken as a preventive med. Otc meds have variable success rates.

14 - 21 days: These flare ups can typically last 14 - 21 days. They are often viral in nature and can recur over and over again. Your doctor can recommend how to reduce the frequency and intensity with some medications.