Propolis, a resinous substance collected by bees from various plants, has a long history of use in traditional medicine due to its purported antimicrobial and anti-inflammatory properties. In recent years, several scientific studies have investigated its efficacy against herpes simplex virus (HSV) infections, particularly herpes labialis (cold sores).

Multiple randomized controlled trials and in vitro studies have demonstrated that propolis extracts possess antiviral activity against HSV-1 and HSV-2. For example, a double-blind, randomized clinical trial published in 2010 found that a 0.5% propolis ointment was more effective than acyclovir ointment in reducing healing time and alleviating symptoms of herpes labialis. Other laboratory studies have shown that propolis can inhibit the replication of herpes viruses and reduce viral load. The proposed mechanisms include disruption of viral envelope integrity and inhibition of viral DNA synthesis.

However, while these results are promising, the number of well-designed clinical trials is limited, and variability in propolis composition can affect reproducibility. Current evidence suggests that propolis may be a useful adjunct or alternative for topical management of mild herpes infections, but more robust clinical data are needed to establish standardized dosing and long-term safety.