Blood root was a traditional remedy of the native North American Indians who used it to treat fevers and rheumatism, to induce vomiting and as an element in divination[254]. In modern herbalism it is chiefly employed as an expectorant, promoting coughing and the clearing of mucus from the respiratory tract[254]. The root is locally anaesthetic, cathartic, emetic, emmenagogue, expectorant, diuretic, febrifuge, sedative, stimulant, tonic[4, 21, 46, 165]. It is taken internally in the treatment of bronchial, respiratory tract and throat infections, and poor peripheral circulation[238]. Use with caution and preferably only under the guidance of a qualified practitioner[238]. The root is toxic[21, 165, 222], containing a number of opium-like alkaloids that are also found in other members of this family[213, 238]. An excessive dose depresses the central nervous system, causes nausea and vomiting, and may prove fatal[238]. This remedy should not be prescribed for pregnant or lactating women[238]. Externally, the root is used in the treatment of skin diseases, warts, nasal polyps, benign skin tumours, sore throats and chilblains[238]. An infusion of the root or the sap of the fresh root is used[207]. The root can be harvested in the autumn, dried and stored for later use. It should not be allowed to become damp since it will then deteriorate[4, 213]. Sanguinarine, which is obtained from the root, is used as a dental plaque inhibitor[238]. The root is used to make a homeopathic remedy that is used to treat migraine[238]. The US FDA has approved the inclusion of one of the active constituents, sanguinarine, in toothpaste as an antibacterial and antiplaque agent [301].