Eating pineapple usually does not cause mouth ulcers to occur, the occurrence of mouth ulcers may be affected by psycho-psychological factors, dietary factors, etc., as follows. In the consumption of pineapple, pineapple within the pineapple bromelain has a certain stimulation of the oral mucosa, destruction of the role of the oral mucosa, may cause pain in the oral mucosa, but usually does not cause mouth ulcers. The specific etiology of oral ulcers is not clear, and may be related to psychosomatic factors, such as anxiety, tension, etc. It may also be related to dietary factors, such as the body’s lack of iron, zinc, vitamins B1, B2, B12 and other nutrients, or long-term consumption of pickled, barbecued, fried foods. The occurrence of mouth ulcers may also be related to other factors, and it is recommended to visit a hospital to receive professional treatment.