Citronella oil

Citronella oil is one of the essential oils obtained from the leaves and stems of different species of Cymbopogon. The oil is used extensively as a source of perfumery chemicals such as citronellal, citronellol and geraniol. These chemicals find extensive use in soap, perfumery, cosmetic and flavouring industries throughout the world.^[1]

Citronella oil is also a renowned plant-based insect repellent, and has been registered for this use in the United States since 1948.^[2] The EPA considers oil of citronella as a biopesticide with a non-toxic mode of action.^[3] Research also shows that citronella oil has strong antifungal properties,^[4][5] and effective in calming barking dogs.^[6]

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Types

Citronella oil is classified in trade into two chemotypes:^[7]

• Ceylon type (obtained from Cymbopogon nardus Rendle) consists of geraniol (18-20%), limonene (9-11%), methyl isoeugenol (7-11%), citronellol (6-8%), and citronellal (5-15%).

• Java type (obtained from Cymbopogon winterianus Jowitt) consists of citronellal (32-45%), geraniol (11-13%), geranyl acetate (3-8%), limonene (1-4%). The higher proportions of geraniol and citronellal in the Java type make it a better source for perfumery derivatives.^{[8] [9]} The name Cymbopogon winterianus is given to this selected variety to commemorate Mr. Winter—an important oil distiller of Ceylon, who first cultivated and distilled the Maha Pangeri type of citronella in Ceylon.

Both types probably originated from Mana Grass of Ceylon, which according to Finnemore (1962) occurs today in two wild forms--Cymbopogon nardus var. linnae (typicus) and C. nardus var. confertiflorus. Neither wild form is known to be used for distillation to any appreciable extent.

Citronella oil from Cymbopogon species should not be confused with other similar lemony oils from Corymbia citriodora and Pelargonium citrosum.

World production

At present, the world production of citronella oil is approximately 7,000 tonnes, the bulk of which is produced in Taiwan, Guatemala, Honduras, Indonesia, Brazil, China, Sri Lanka, India, Argentina, Ecuador, Madagascar, Mexico and the West Indies.

Use as an insect repellent

Citronella oil is popular as a 'natural' insect repellent. Its mosquito repellent qualities have been verified by research,^[10] including effectiveness in repelling Aedes aegypti. ^[11][12] However, most citronella repellent formulas applied to the skin require reapplication after 30-60 minutes to remain efficient.^[13]

Safety as repellent

Citronella may irritate skin and cause dermatitis in certain individuals. It should not be used on the skin of young children (under 3 years old).

The US Environmental Protection Agency states that citronella oil has little or no toxicity when used as a topical insect repellent, with no reports of adverse effects of concern over a 60 year period. Because some products are applied to human skin, EPA requires proper precautionary labeling to help assure safe use. If used according to label instructions in the US, citronella is not expected to pose health risks to people, including children and other sensitive populations.^[14] The US Food & Drug Administration consider citronella oil as generally recognized as safe (GRAS).

Canadian regulatory concerns with citronella as an insect repellent are primarily based on data-gaps in toxicology, not on incidents.^{[15] [16]} In Europe, Ceylon type citronella oil is placed on the category 3 list, with some safety concern regarding methyl eugenol.^[17]

References