Citronella oil is an essential oil obtained from the leaves and stems of different species of Cymbopogon (lemongrass). The oil is used extensively as a source of perfumery chemicals such as citronellal, citronellol, and geraniol. These chemicals find extensive use in soap, candles and incense, perfumery, cosmetic, and flavouring industries throughout the world. Citronella oil is also a plant-based insect repellent and has been registered for this use in the United States since 1948.

Source: Wikipedia