Vomiting is caused by upward adverse flow of gastric qi. Inspection of vomitus is helpful for understanding the cause of upward adverse flow of gastric qi and the nature of disease.

Thin vomitus without foul smell indicates cold syndrome due to consumption of gastrosplenic yang or invasion of pathogenic cold in the stomach. Turbid and sour vomitus indicates heat syndrome due to exuberant heat in the stomach or liver fire attacking the stomach. Sour and fetid vomitus with indigested food accompanied by unpressable abdominal distension and pain is caused by retention of food due to intemperance of food and indigestion. Vomiting of indigested food without sour and fetid smell is caused by asthenic cold in the spleen and stomach. Vomiting of clear fluid, sputum and saliva is usually due to dysfunction of the spleen due to retention of fluid in the stomach.

Vomiting of yellowish and greenish bitter fluid is due to accumulation of damp heat in the liver and gallbladder or due to adverse flow of liver and gallbladder qi which invades the stomach. Vomiting of fresh blood or purplish blood with clot or with food dregs is often due to impairment of the collaterals by stomach heat and liver fire or blood stasis in the epigastrium. Vomitus with pus and blood indicates stomach abscess due to accumulation of heat toxin in the stomach and putrefaction of blood stasis.