Wild indigo is a heat-clearing, anti-viral herb that is used to remove heat and toxins in such conditions as boils, abscesses, and septicemia. Wild indigo is also indicated for laryngitis and tonsillitis. Externally, it is applied as a poultice to sore or cracked nipples. It is widely used in Europe and the U.S. in combination with echinacea and thuja in immune stimulant preparations to treat colds and flu, especially when accompanied by a fever.