Measles, eczema treated with TCM Dictamnus Root Bark

What is Bai Xian Pi(Dictamnus Root Bark)?
Actually it refers to the rhizome of Dictammnus dasycarpus Turcz, which has a variety of other names such as Dictamnus albus., Fraxinella, Adiptam, Herba Dictamni Herba., Gas Plant, and Dittany. Burning Bush is a perennial herbaceous plant and with peculiar irritant odor. It has yellowish white ligneous roots in tight clusters. Stems are erect, 50 to 65cm high. Alternate pinnately compound leaves are oval or oblong elliptic in shape, 3.5 to 9cm long, and 2 to 4cm long. And it has racemose flowers, rachis and pedicel mixed white pubescence and black glandular hair, and pink with purple red lines. The fruit is capsule, densely covered with glandular hairs, splitting into 5 segments at maturity, one prickle at the end of each segment, and 2 to 3 round black seeds inside. Flower season is April and May. Fruiting time is May to June. It grows in hillside or woods.

As a frequently used herb for healthy skin in TCM remedies, its medicinal part is dictamnus root bark, which is collected in spring and autumn in the North and summer in the East in China. The process is to dig it out, remove fibril and tertia, split lengthways when it is still fresh, take out the woodent heart, and dry in the sun.

The dried rhizome presents coiling block or double barrels in shape, 7 to 12cm long, 1 to 2 in diameter, 2 to 5mm thick, yellowish white to light brown surface, slightly smooth, and with vertical wrinkles and lateral root scars. Internal surface is light yellow, smooth, and with round holes caused by branch roots. It is crisp and easy to break, with ivory and layered cross section. Put under the sunlight or lamp, small white sparkling crystals is seen. It smells like mutton and tastes slightly bitter. Medicinally the preferred one is in coiling block, without woodent heart, thick bark, and large in size. And it is mainly produced by provinces of Liaoning, Hebei, Sichuan, Jiangsu, Zhejiang, and Anhui.

Why it treats skin problems?
According to theory of Traditional Chinese Medicine (TCM), it is bitter and cold in nature. And it covers a few meridians of spleen, stomach and urinary bladder.

Main functions are to clear heat and dry damp, expel wind and stop itch, and detoxify. Main clinical usage and indications are measles due to the accumulation of wind, heat, and damp, Eczema, scabies, ringworm, jaundice, and pain or numbness caused by damp and heat (arthritis). According modern researches, it is also capable of killing bacterium, diminishing inflammation, benefiting heart, fighting cancer, and contracting uterine smooth muscle. In terms of getting healthy skin naturally, it can remove dark spots, moisten skin and release toxins efficiently.

Regular dosage is 6 to 15 grams in decoction and more used externally.

In TCM practice, Ben Cao Jing Shu (Classic Theory of Materia Medica) said it should not be used in people suffering from cold and deficiency in Lower Jiao although dampness was there. Else, according to Ben Cao Jing Ji Zhu (Collected Annotation of Herbalism), it is incompatible with herbs like Sang Piao Xiao (Ootheca Mantidis), Jie Geng (Balloon Flower Rhizome), Fu Ling (Poria), and Bi Xie (Yam Rhizome).