St. John's Wort is an herbal medicine used to treat mild to moderate depression, anxiety, and infections. It is also used to increase memory aaand concentration. St John's Wort can be used on the skin to help heal wouunds and to control pain. Other names for St. John's Wort include: Hypericum perforatum and Saint John's Wort. Check with your doctor before taking St. John's Wort.