Ascaris lumbricoides is harmful to human body in many ways, the common ones are can cause pneumonia, malnutrition, intestinal ascariasis, ascaris intestinal obstruction and so on. The larvae of Ascaris lumbricoides migrate in the lungs in the early stage, which will cause pneumonia, and its main manifestations include fever, cough, and foreign body sensation in the pharynx. Ascaris lumbricoides resides in the human body, it will consume the nutrition of human body, which will cause malnutrition in the long run. Adult Ascaris lumbricoides reside in the small intestine causing intestinal ascariasis, whose main symptoms include abdominal pain, diarrhea, deepening around the umbilicus, poor appetite, constipation, and so on, and children may also suffer from teeth grinding, irritability, and other manifestations. When roundworms gather and twist in the small intestine, it will cause intestinal obstruction. There are many other harmful effects of roundworms, such as ectopic ascariasis, biliary ascariasis, appendicular ascariasis, and roundworm metastasis. If you suspect a roundworm infection, it is recommended to go to the hospital in time to avoid delay.