Bitter

苦 kǔ, bitter herbs have a downwards-moving action that can be used to purge excess pathogens through the stool, eliminating fire and heat, sedating rising qi, and dry dampness.

Some examples include rhubarb root (da huang, Rheum officinale), baikal skullcap (huang qin, Scutellaria baicalensis), coptis (huang lian, Coptis chinensis), sophora (ku shen / huai hua, Sophora flavescens) and gardenia (zhi zi, Gardenia jasminoides).

Their drying nature means bitter herbs should be used with caution where there is deficiency of yin and body fluids and their purging, cooling properties indicate caution with cold pathogens or Spleen qi deficiency, which can further deplete Spleen qi and cause gastrointestinal reactions.