Isatis indigotica is the dry root of Isatis indigotica, a cruciferous plant. It is usually dug in autumn and can be used as medicine after processing. It is produced all over China. Radix Isatidis can be divided into Radix Isatidis and Radix Isatidis; The rhizome and root of Baphicacanthus cusia (Nees) Brem. It is cold in nature, slightly sweet in taste and then bitter and astringent. It has the effect of clearing away heat and toxin, preventing colds and throat. It is mainly used for the treatment of mild toxic hair spot, dark purple tongue, rotten throat Dan Sha and other diseases.