Anal oil may be caused by episodic overnutrition or by anorectal diseases. Occasional overnutrition is mainly caused by patients consuming a large amount of overly oily food in a short period of time, such as large fish, meat, barbecue, fried food, and consuming too much oil, which is not fully absorbed by the gastrointestinal tract and excreted through the feces, resulting in the symptoms of oil in the anus. Anal diseases, such as intestinal digestion and malabsorption caused by enteritis, food is discharged before it is completely digested, and the symptoms of oil flow will appear. Anal fistula due to fecal and rectal mucus flowing outside the anus, hemorrhoids, especially internal hemorrhoids with mucus-like secretions on the surface, and abnormal secretions caused by perianal eczema can also appear similar to the appearance of oil-like fluid at the anal opening, causing the feeling of oily flow. It is recommended to carefully observe if there are other symptoms accompanying the appearance, such as diarrhea, bloating, blood in the stool, etc., to provide a valuable basis for the doctor’s diagnosis when seeking medical attention.