There are two main reasons for gas discharge from the anus. One is related to diet, consuming too much food that can produce gas and starchy food, such as sweet potatoes, onions, pasta, desserts, etc., will make the gastrointestinal tract bacteria produce a large amount of gas, increase the number of gastrointestinal peristalsis, resulting in gas discharge from the anus. Irregular diet and untimely meals can lead to poor function of the gastrointestinal tract, causing intestinal disorders, increased gas production and gas discharge from the anus. Another reason is to suffer from certain diseases that can promote anal discharge, such as irritable colon syndrome, gastritis, peptic ulcer, peptic bleeding, dysentery and so on. However, if the anus does not discharge gas for a long time, there are usually lesions in the gastrointestinal tract, such as rectal cancer, intestinal obstruction, hemorrhoids, intussusception and other gastrointestinal diseases.