Lysine may shorten the duration, but not the severity, of cold sore outbreaks, according the WebMD. Lysine ointment may be topically applied to the sore, or lysine supplement pills may be taken internally. A typical dose to treat cold sores is 1,000 milligrams of oral lysine per day.
A study conducted in 2005 showed that 40 percent of patients who used a lysine-based ointment experienced relief of cold sore symptoms after three days, reports About.com. By the sixth day of the study, 87 percent of patients were cleared of cold sores. This compares favorably with untreated cold sores, which typically last about three weeks.
Alternately known as L-Lysine monohydrochloride, lysine may stop the replication of the herpes simplex labialis virus that causes cold sores, states About.com.