When Dampness weighs down digestion
A feeling of heaviness and fullness after meals, a flagging appetite, a pasty mouth, a tongue with a thick coating, a heavy, listless body, especially in damp weather… In TCM, these signs may be associated with Dampness settled in the Middle Burner: it clogs the Spleen, which no longer transforms food, and the Stomach, which no longer sends downwards. Qi then stays stuck in the middle.
Ping Wei San, the “Powder that Levels the Stomach”, first appeared under the Northern Song in the Jian Yao Ji Zhong Fang (《简要济众方》) by Zhou Ying (周应), then entered the Tai Ping Hui Min He Ji Ju Fang (《太平惠民和剂局方》), the imperial formulary, whose version became the reference. “Levelling” is just the right word: according to the commentators, a centre soaked with Dampness rises up like waterlogged ground, and the formula brings it back to level. It is the base of a whole family of formulas: Huo Xiang Zheng Qi Wan, for example, takes up its magnolia bark and tangerine peel.
One dries, the other moves forward
The heart of the formula is a pair. Atractylodes, the most highly dosed herb, dries Dampness and restores the Spleen’s transporting function; magnolia bark sets Qi moving and makes it descend. According to tradition, Dampness and blocked Qi feed each other: one slows Qi down, and Qi that does not move lets Dampness accumulate. The formula breaks this circle from both ends.
Dries Dampness: Atractylodes, bitter, pungent and warm, is among the strongest herbs in the Chinese materia medica for drying Dampness. It addresses the cause.
Harmonises the Stomach: Magnolia bark makes Qi descend and restores the Stomach’s natural direction; tangerine peel, lighter and aromatic, awakens the Spleen.
Promotes a feeling of lightness: Three of the four herbs are aromatic and warm: they awaken a centre made sluggish by Dampness, and licorice softens them to spare the Spleen.
