Lemon (Citrus limon) is a type of citrus fruit. It contains high levels of citric acid. The fruit, juice, and peel are used to make medicine. Lemon contains antioxidants called bioflavonoids. These bioflavonoids might be responsible for the health benefits of lemon. People use lemon for hay fever, high blood pressure, obesity, morning sickness, and many other conditions, but there is no good scientific evidence to support these uses. Do not confuse lemon with other citrus fruits, such as grapefruit, lime, and sweet orange.