Licorice (Glycyrrhiza glabra
) contains glycyrrhizin (or glycyrrhizic acid), which has a long history of use in ethnoveterinary medicine.
Licorice has been used since 500 BC for the treatment of peptic ulcers, asthma, pharyngitis, malaria, abdominal pain, and infections.
possesses some antiviral activity in vitro
toward a number of viruses---including Newcastle disease virus (NDV)
in chickens and Duck Hepatitis Virus (DHV) in ducks. In a study conducted on 40 day-old white Pekin domestic ducklings, treatment with glycyrrhizin alone or with DHV vaccine demonstrated to be an effective immune system booster and had an antiviral effect against DHV.