Ascariasis is mainly caused by the ingestion of food carrying eggs of roundworms. The parasitism of roundworms inside the human body blocks intestinal tract, causes functional disorder of qi activities. In this case, disorder of the stomach qi will result in the gastric failure in transportation and transformation, giving rise to nausea, poor appetite, abdominal pain, etc.. Besides, roundworms are fond of moving around. If stimulated by cold, heat, food, etc., they will be liable to move from one part to another inside the intestine. If they go into the biliary tract, colic due to ascariasis may occur. Finally, if roundworms form the shape of a ball, it will obstruct intestinal tract, developing into abdominal mass of roundworms.