Drain dampness (xie shi)

Herbs that drain dampness regulate water metabolism, leach out dampness and promote urination. This includes the removal of accumulated water in oedema, thin mucus obstructing the respiratory and digestive systems, and damp-heat disorders where the obstruction is accompanied by burning sensations or fever such as urinary obstruction, weeping sores and jaundice. They also treat phlegm, where damp stagnation is a significant factor.

Common examples include fu ling (poria, Poria cocos), zhu ling (umbrella polypore, Polyporus umbellatus), ze xie (water plantain, Alisma orientalis) and che qian zi (plantain seed, Plantago orientalis). Their draining action can also deplete yin so should be used cautiously in deficiency.