The present invention relates to the use of a casein hydrolysate as an antiherpetic agent. This casein hydrolysate has an application in both the treatment and the prevention of the reactivation of a latent infection by a herpesvirus, and is effective both orally and topically. It also relates to a pharmaceutical composition in the form of cream, gel, ointment or paste for topical administration that contains it.USO DE UN HIDROLIZADO DE CASEÍNA PARA PREPARAR UN MEDICAMENTO ÚTIL EN LA PREVENCIÓN Y/O TRATAMIENTO DE INFECCIONES CAUSADAS POR HERPESVIRUS.