Prunella refers to the Chinese herb xiakucao (literally: weed that withers in summer; its purple-flowered spikes turn reddish brown during the summer). The herb material is obtained from the plant Prunella vulgaris, which grows across much of the temperate zone of the northern hemisphere. It is produced in most places in China, though mainly collected in Jiangsu, Anhui, and Henan Provinces (Huang 1996). The dried spikes are collected in summer. Prunella is classified as an herb for clearing heat and purging fire, considered to have its primary effect on the syndrome of "liver fire.” It falls under the fire-purging classification because of its use in treating redness and inflammation of the eyes or infections of the skin. However, it is also one of the herbs that regulate the circulation of qi, mainly given for resolving accumulations and masses; being of light nature, it is especially used for accumulations in the upper body (chest, throat, and head).