Onions are irritating to the stomach, so you should try to avoid eating raw onions on an empty stomach. Onion contains vitamins, volatile oil, cellulose, oak bark flavin and other nutrients, the smell is relatively pungent, with the effect of dispersing wind and cold. In the uncooked state onions contain a lot of pungent substances, this substance into the stomach will cause some stimulation of the mucosa of the stomach wall, too much intake will lead to stomach wall spasm, contraction, and even painful phenomenon. Therefore, you should avoid eating onions on an empty stomach, and it is best to eat them together with food to avoid the pungent substances of onions coming into direct contact with the gastric mucosa. Patients suffering from gastritis and gastric ulcer should also heat the onion before eating it. The nutrients of onion will not disappear after heating, and the irritation will also be reduced, which can avoid the damage caused to the stomach wall.