The reason why lemons smell like lemons, the reason why oranges smell like oranges.
Limonene is common in cosmetic products. As the main odor constituent of citrus, D-limonene is used in food manufacturing and some medicines, e.g. as a flavoring to mask the bitter taste of alkaloids, and as a fragrant in perfumery; it is also used as botanical insecticide. It is added to cleaning products such as hand cleansers to give a lemon-orangefragrance.