St. Johns wort has been used in herbal healing for more than 2,000 years, most notably for its ability to speed wound healing. And only recently scientists have gathered some evidence on the herb's possible effectiveness as an immune system stimulant.

But its most exciting potential medical use was discovered in 1998, when researchers at New York University and the Weizmann Institute found it has "dramatic" activity against a family of viruses that includes HIV.

The leaves and flowers of St. Johns wort contain special glands that release a red oil when pinched. Early Christians named the plant in honor of John the Baptist, because they believed it released its blood-red oil on August 29, the anniversary of the saint's beheading. (Wort is Old English for plant.)

In the first century, the Roman naturalist Pliny prescribed St. Johns wort in wine as a cure for the bites of poisonous snakes. And the Greek physician Dioscorides recommended it externally for burns and internally as a diuretic, menstruation promoter, and treatment for sciatica and recurring fevers (malaria). The Greeks and Romans also believed the herb was a protector against witches' spells.

Under the Doctrine of Signatures—the medieval belief that herb's physical appearance revealed their healing value&mdashred plants were believed to be good for wounds, and "the juicy red flower" of St. Johns wort was no exception. In the 16th century John Gerard recommended it as a "most precious remedy for deep wounds," and wrote the herb "provoketh urine and is right good against stone in the bladder."

The first London Pharmacopoeia in 1618 advised chopping St. Johns wort flowers, immersing them in oil, and placing the mixture in the sun for three weeks. The resulting tincture was a standard treatment for wounds and bruises for several hundred years.

Early colonists introduced St. Johns wort into North America but found the Indians using the native American herb in much the same way Europeans used the Old World plant—as a tonic and treatment for diarrhea, fever, snakebite, wounds, and skin problems.

Throughout the 19th century, homeopathy was a popular as orthodox medicine, and homeopaths prescribed the herb for a variety of ailments: wounds, asthma, bites, sciatica, diarrhea, hemorrhoids, and certain forms of paralysis. Contemporary homeopaths continue this tradition.

America's 19th-century Eclectic physicians also considered St. Johns wort a useful wound treatment and tetanus preventive and advocated the whole herb a treatment for "hysteria" (menstrual discomforts) because of its "undoubted power over the nervous system and spinal cord."

Several studies have supportedSt. Johns wort's traditional use in the wound healing. The hypericin and other antibiotic chemicals in the herb's red oil may help prevent wound infection. In addition, the plant's potential immune-stimulating flavonoids help reduce wound inflammation. One German study showed that compared with conventional treatment, a St. Johns wort ointment substantially cut the healing time of burns and caused less scarring. (This product is not available in the United States.)