A common herb may provide a new and effective treatment for the sexually transmitted infection herpes.
Prunella vulgaris has been used to treat cancer
Scientists have successfully used an agent derived from the herb, Prunella vulgaris, to prevent the disease in animals.
The herb, commonly found in Britain, Europe, China and North America, has been used in the past to treat sores in the mouth and throat.
There is also some evidence that it has been used as a crude anti-cancer drug and to lower high blood pressure.
Dr Song Lee and his colleagues from Dalhousie University in Nova Scotia, Canada, extracted a compound from the plant.
This was then added to a cream and tested on mice and guinea pigs who had been infected with two types of the herpes simplex virus.
Use of the cream significantly cut the death rate among mice, and the development of skin lesions in guinea pigs.
Dr Lee said the plant extract - a lignin-carbohydrate compound - acted in a way different to that of the current anti-herpes drug, acyclovir.
He said: "Given the high incidence of herpes infection and the emergence of acyclovir-resistant strains of herpes viruses, the Prunella lignin-carbohydrate complex may prove to be a useful new anti-herpes drug."
A spokesperson for the UK Health Protection Agency said: "This new treatment looks promising, but will require human trials before it can be widely used."
The number of cases of herpes simplex virus infection recorded by specialist clinics jumped by nine times in women, and doubled in men between 1972 and 2001.
In 2001, 17,850 new cases diagnosed in England, Wales and Northern Ireland.
The highest rate of infection was recorded in the 20 to 24 year old age group.
Details of the research were presented at a meeting of the American Society for Microbiology.