Limited evidence for benefits of interventions in preventing cold sores

Long-term use (>1 month) of antiviral drugs taken by mouth resulted in a small decrease in cold sores (eg, from 1.80 to 0.85 episodes per participant over 4 months). The preventive effect of long-term use of aciclovir cream applied to the lips was uncertain. Short-term use of either antiviral drugs or creams did not prevent cold sores. Neither short-term nor long-term use of these antiviral drugs or creams appeared to cause side effects. The preventive effects of sunscreen were uncertain. There was very little evidence about the preventive effects of thymopentin, low-energy laser and hypnotherapy. There were no preventative effects of lysine, LongoVital supplementation, gamma globulin, herpes virus vaccine, yellow fever vaccine, levamisole or interferon. Application of sunscreen prevented cold sores induced by experimental ultraviolet light, but did not prevent cold sores induced by sunlight.