Acyclovir prevents reactivation of herpes simplex labialis in skiers

Abstract
To determine the effectiveness of an antiviral to prevent herpes labialis during a brief, high-risk circumstance, 147 persons with a history of sun-induced recurrences were treated prophylactically with oral acyclovir or matching placebo and were observed during their ski holidays. Five (7%) of 75 acyclovir-treated subjects developed lesions compared with 19 (26%) of 72 persons in the placebo group. (JAMA1988;260:1597-1599)