Lichen, particularly species such as Usnea or Cetraria, has been used in traditional herbal medicine for various ailments, including infections. The use of lichen preparations to treat or support herpes is primarily rooted in traditional practices, especially in European and Asian folk medicine, where lichens have been valued for their purported antimicrobial and antiviral properties. However, direct historical records specifically linking lichen to herpes treatment are sparse; more commonly, lichens were used for general skin ailments, wounds, or as broad-spectrum remedies for infectious diseases.

Modern scientific studies investigating lichens have identified some compounds, such as usnic acid, that exhibit antiviral activity in vitro. However, robust clinical evidence supporting the efficacy of lichen extracts against herpes simplex virus (HSV) in humans is lacking. Most research is preliminary, conducted in laboratory settings rather than through clinical trials. As such, while there is a traditional basis for the use of lichen in treating skin conditions and infections, there is insufficient scientific validation for its specific use against herpes.

In summary, the use of lichen for herpes is justified mainly by tradition, with limited and indirect scientific support. The strength of evidence is weak, primarily due to the absence of high-quality clinical studies.