Lysine is thought to interfere with arginine being absorbed into your intestine, making the amino acid unavailable for the virus. So even if it may not cure a cold sore infection, lysine can help slow or prevent the HSV-1 replication process. In addition, older researchTrusted Source suggests that lysine may reduce the number of occurrences of this infection and decrease healing time. For example, a small study from 2005Trusted Source showed that lysine sped up the healing process for 87 percent of participants, shortening the average time from 21 days to 6 days for these people.