What is daily suppressive therapy for cold sores?

Daily suppressive therapy means taking an antiviral drug, typically valacyclovir or acyclovir, every day to reduce HSV-1 replication and cut herpes labialis outbreak frequency by up to 78%. The limitation: suppression addresses the virus internally but leaves the lip barrier completely exposed. UV radiation is a documented HSV-1 reactivation trigger, and most lip balms compound this with menthol or camphor that irritate compromised epithelium. A 22% zinc oxide barrier like Labisan SPF 20 blocks the UV trigger at the surface and seals the skin, closing the gap antivirals cannot reach.