Oil in the stool may be caused by the patient suffering from functional dyspepsia, steatorrhea, rectal cancer, or gastroenteritis or food allergies. Patients have functional dyspepsia due to eating too much greasy food, too many fried products are not completely digested in the abdominal cavity, and the oil is excreted along with the stool without complete digestion. It is also possible to produce steatorrhea, or oily diarrhea, where the digestive and absorption functions of the small intestine are reduced and nutrients are not completely absorbed, also known as dyspepsia syndrome, which arises from eating things that are too sour or cold or spicy, and poor absorption in the digestive tract leading to excretion of stools with oil. In addition, if the rectal cancer may be caused by long-term improper diet, there will also be oil in the stool, and patients with gastroenteritis and food allergies will also have oil in the stool.