Skullcap is the herb of a member of the mint family from rich woods and moist soils in eastern North America. Another commonly used species is Baikal skullcap, (S. baicalensis), the root of which is the Chinese drug huang-qin. It is found in sandy fields in northeast China and adjacent Russia and in the mountains of south west China.
Also known as maddog skullcap, the American species was historically used to treat rabies. Traditionally it is known as a nerve tonic and sedative for relieving anxiety, neuralgia, and insomnia. Baikal skullcap was first mentioned in the middle class of drugs in Shen Nong Ben Cao Jing. In China it is found in prescriptions for fevers, colds, high blood pressure, hypertension, insomnia, headache, intestinal inflammation, vomiting of blood, and other conditions.
Almost all recent research has been done on the Chinese S. baicalensis. Few studies have been done on American skullcap, but one of its compounds, scutellarin, has been shown to have mild sedative and antispasmodic properties. Baikal skullcap, the subject of numerous Chinese studies, inhibits bacteria and viruses, is diuretic, and lowers fevers and blood pressure; in China, it is used to treat hepatitis. One flavonoid found in the root, baicalin, has similar properties. Clinical studies in China show that a tincture of Baikal skullcap reduces high blood pressure.
American skullcap is a good candidate for further research.
Skullcap is available in dried form as teas, capsules, tablets, and tinctures. Care should be taken to buy skullcap from a reliable source to ensure the identity of the plant material.
Recently several herbs, including European products containing germander (Teucrium chamaedrys), have been linked to liver damage. The North American native germander (T. canadensis), also known as wood sage or wild basil, has traditionally been used to induce menstruation, urination, and sweating. It is widely seen as an adulterant in commercial supplies of skullcap (S. lateriflora). Reports of liver toxicity related to skullcap may actually involve the adulterant, which is traded as "pink skullcap". Two cases of "skullcap" poisoning, including one fatality, were reported from the Riks Hospital in Oslo, Norway, in 1991. It is unclear whether the offending herb was S. lateriflora or a species of Teucrium.