Onion (Allium cepa L.) is a biennial vegetable of the Allium genus in the Liliaceae family. Onions are rich in flavonoids, steroidal saponins, phenylpropanoids, prostaglandins, sulfur-containing compounds, and nitrogen-containing compounds, with extremely high nutritional and medicinal value. They can inhibit pathogenic microorganisms and have effects such as lowering blood pressure, blood lipids, cholesterol, antioxidant, and anti-cancer.