This popular citrus fruit is a 'hesperidium'; a fleshy fruit with a leathery rind. Oranges are an excellent source of Vitamin C and a good source of folate and potassium. They are low in kilojoules and provide 'pectin' which may help control blood cholesterol levels. Orange peel contains 'limonene', an oil which is a common allergen, and may also be treated with sulphites which can trigger allergic reactions in some. Originating in Asia, a number of languages refer to the orange as "China's apple".