Four Qi refers to four different properties of drugs: cold, hot, warm and cool. Each traditional Chinese medicine has different four Qi and five flavors, so it has different therapeutic effects. The theory of "Four Qi and Five Flavors" was first published in Shennong's Classic of Materia Medica, and its preface said: "Drugs have five flavors: sour, salty, sweet, bitter and pungent, and cold, hot and warm."

The drugs represented by the five flavors are all irritating. It has the functions of dispersing stagnation, relieving exterior syndrome, promoting qi circulation and promoting blood circulation. 2 sweetness. It can tonify and slow down, and has the functions of nourishing, harmonizing and combining medicinal properties and relieving pain. 3 sour taste. Can converge, and has the effects of convergence and astringency. 4 bitterness. It can relieve energy, dry and firm, and clear away heat. 5 salty. Has the effects of relaxing bowels, softening hard mass and resolving hard mass.