Once in the blood, valacyclovir starts to work almost immediately. Since it specifically attacks the DNA replication process, it will only attack herpes viruses that are reproducing. So while valacyclovir starts to work on an active infection very quickly, it will not fight the virus that is inactive and hiding in the nervous system.
Though valacyclovir starts working quickly, the symptoms and sores of an actual outbreak may take days to begin to heal and the virus can stay active throughout the healing process. Please see the full Prescribing Information here.
This information is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment, and should never be relied upon for specific medical advice. If you have any questions or concerns, please talk to your healthcare provider.