Lei wan

A patient passing tapeworm segments, with a hungry but wasting appetite and vague periumbilical discomfort

A thin child with a big belly, sallow face, poor appetite, and worms seen in the stool

Roundworm colic with intermittent umbilical pain and a good appetite between attacks

Overview. Lei wan is not a plant but a fungus: the hard, potato-like sclerotium of Omphalia lapidescens, which forms underground among bamboo roots in the mountains of central and southwestern China. The sclerotia are dug in autumn, washed, and dried. It is a cold, slightly bitter drug of the Stomach and Large Intestine channels and the classic Chinese taeniacide. Its active principle is a proteolytic enzyme, which dictates how it must be prepared and taken.

Clinical Notes. Lei wan is the one worm herb that must never be boiled. Its activity comes from a protease destroyed by heat above about sixty degrees and active only in the neutral to mildly alkaline small intestine, so the sclerotium is ground to a fine powder and swallowed with warm, not hot, water after meals.

Chinese Medicine Profile. Temperature: cold. Taste: slightly bitter. Channels: Stomach, Large Intestine. Actions: Kills intestinal worms, especially tapeworm; Disperses food and worm accumulation in the intestines; Relieves abdominal pain and distension caused by parasites; Restores appetite and growth in children wasted by worms.

Conservation. Sclerotia are mostly wild-harvested from bamboo forests and the resource is under pressure; cultivation methods are being developed, so prefer cultivated or sustainably sourced material where it can be found.