Citronella oil 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 Citronellal or rhodinal ( C10 H18 O) is a monoterpenoid aldehyde, the main component in the mixture of terpenoid chemical compounds that give citronella oil its distinctive lemon scent. Citronellal is a main isolate in distilled oils from the p ...

citronellol Citronellol, or dihydrogeraniol, is a natural acyclic monoterpenoid. Both enantiomers occur in nature. (+)-Citronellol, which is found in citronella oils, including ''Cymbopogon nardus'' (50%), is the more common isomer. (−)-Citronellol is w ...

, and

geraniol Geraniol is a monoterpenoid and an alcohol. It is the primary component of citronella oil and is a primary component of rose oil, palmarosa oil. It is a colorless oil, although commercial samples can appear yellow. It has low solubility in w ...

. These chemicals find extensive use in soap,

candles A candle is an ignitable wick embedded in wax, or another flammable solid substance such as tallow, that provides light, and in some cases, a fragrance. A candle can also provide heat or a method of keeping time. A person who makes candles ...

and

incense Incense is aromatic biotic material that releases fragrant smoke when burnt. The term is used for either the material or the aroma. Incense is used for aesthetic reasons, religious worship, aromatherapy, meditation, and ceremony. It may also b ...

, perfumery, cosmetic, and flavouring industries throughout the world. Citronella oil is also a plant-based

insect repellent An insect repellent (also commonly called "bug spray") is a substance applied to skin, clothing, or other surfaces to discourage insects (and arthropods in general) from landing or climbing on that surface. Insect repellents help prevent and cont ...

and has been registered for this use in the United States since 1948. The

United States Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it ...

considers oil of citronella as a

biopesticide A Biopesticide is a biological substance or organism that damages, kills, or repels organisms seens as pests. Biological pest management intervention involves predatory, parasitic, or chemical relationships. They are obtained from organisms inclu ...

with a non-toxic mode of action. Citronella oil has strong antifungal properties.

Types

Citronella oil is classified in trade into two chemotypes:Chang, Yu Shyun, 2007, ''8 Map species from Malaysia for ICS,'' Forest Research Institute Malaysia, Workshop on NFP, 28–29 May 2007, Nanchang, PR China

Ceylon type

* CAS: 89998-15-2 * CAS: 8000-29-1 * EINECS: 289-753-6 * FEMA: 2308 * CoE: 39 * Obtained from: ''

Cymbopogon nardus ''Cymbopogon nardus'', common name citronella grass, is a species of perennial aromatic plant from the family Poaceae, originating in tropical Asia. It is the source of an essential oil known as citronella oil, which is widely used for its natu ...

'' Rendle * Main components:

(5–15%),

(18–20%) and

geranyl acetate Geranyl acetate is a monoterpene. It is a colorless liquid with a pleasant floral or fruity rose aroma. It is a colorless liquid but commercial samples can appear yellowish. Geranyl acetate is insoluble in water but soluble in organic solvents. S ...

(2%),

(6–8%),

limonene Limonene is a colorless liquid aliphatic hydrocarbon classified as a cyclic monoterpene, and is the major component in the oil of citrus fruit peels. The -isomer, occurring more commonly in nature as the fragrance of oranges, is a flavoring a ...

(9–11%), and

methyl isoeugenol Methyl isoeugenol (isomethyleugenol) is a phenylpropanoid, the methyl ether of isoeugenol, found in certain essential oils. It can occur as both (''E'')- and (''Z'')-isomers. See also * Methyl eugenol Methyl eugenol (allylveratrol) is a na ...

(7–11%).

Java type

* CAS: 91771-61-8 * CAS: 8000-29-1 * EINECS: 294-954-7 * FEMA: 2308 * CoE: 2046 * Obtained from: '' Cymbopogon winterianus'' Jowitt * Main components:

(32–45%),

(21–24%) and

(3–8%),

(11–15%),

(1–4%). The higher proportions of

and

in the Java type oil make it a better source for perfumery derivatives. The standard quality of Java type from Indonesia is regulated by Indonesian authority under SNI 06-3953-1995, which requires

minimum 35% and total

minimum 85%. Both types probably originated from Mana Grass of Sri Lanka, 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 Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the heat ...

to any appreciable extent. Citronella oil from Cymbopogon species should not be confused with other similar lemony oils from ''

Corymbia citriodora ''Corymbia citriodora'', commonly known as lemon-scented gum and other common names, is a species of tall tree that is endemic to north-eastern Australia. It has smooth white to pink bark, narrow lance-shaped to curved adult leaves, flower buds ...

'' and '' Pelargonium citrosum''.

Health questions

Direct application of citronella oil has been found to raise the heart rate of some people. Health Canada banned the oil's use as an insect repellent in 2012 but later lifted the ban in February 2015.

World production

At present, the world annual production of citronella oil is approximately 4,000

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...

s. The main producers are China and

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

- producing 40 percent of the world's supply. The oil is also produced in

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...

, Guatemala, Honduras,

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

, Sri Lanka,

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

Ecuador Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ' ...

Jamaica Jamaica (; ) is an island country situated in the Caribbean Sea. Spanning in area, it is the third-largest island of the Greater Antilles and the Caribbean (after Cuba and Hispaniola). Jamaica lies about south of Cuba, and west of His ...

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

, and

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...

. The market for natural citronella oil has been eroded by chemicals synthesised from

turpentine Turpentine (which is also called spirit of turpentine, oil of turpentine, terebenthene, terebinthine and (colloquially) turps) is a fluid obtained by the distillation of resin harvested from living trees, mainly pines. Mainly used as a spec ...

derived from conifers. However, natural citronella oil and its derivatives are preferred by the

perfume Perfume (, ; french: parfum) is a mixture of fragrant essential oils or aroma compounds (fragrances), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agreeable scent. Th ...

industry.

Use as a repellent

Citronella oil is popular as a natural insect repellent. Its

mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...

repellent qualities have been verified by research, including effectiveness in repelling ''

Aedes aegypti ''Aedes aegypti'', the yellow fever mosquito, is a mosquito that can spread dengue fever, chikungunya, Zika fever, Mayaro and yellow fever viruses, and other disease agents. The mosquito can be recognized by black and white markings on its le ...

'' ( dengue fever mosquito). To be continually effective, most citronella repellent formulas need to be reapplied to the skin every 30–60 minutes. Citronella candles (which burn citronella oil) are no more effective than other candles at repelling insects, and experts do not recommend it as a useful method. Research also indicates that citronella oil is an effective repellent for

body lice The body louse (''Pediculus humanus humanus'', also known as ''Pediculus humanus corporis'') is a hematophagic ectoparasite louse that infests humans. It is one of three lice which infest humans, the other two being the head louse, and the cr ...

head lice The head louse (''Pediculus humanus capitis'') is an obligate ectoparasite of humans. Head lice are wingless insects that spend their entire lives on the human scalp and feeding exclusively on human blood. Humans are the only known hosts of thi ...

, and stable flies. A study conducted by

DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Ad ...

in 1963 determined that hydroxycitronellal was an effective repellent against both aquatic and terrestrial

leeches Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bo ...

. The US Environmental Protection Agency states that citronella oil has little or no

toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

when used as a topical insect repellent, with no reports of adverse effects of concern over a 60-year period. Some products are applied to human skin, so 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. The US

Food & Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food s ...

considers 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 Toxicology is a scientific discipline, overlapping with biology, chemistry, pharmacology, and medicine, that involves the study of the adverse effects of chemical substances on living organisms and the practice of diagnosing and treating e ...

, not on incidents. In the EU, Ceylon type citronella oil is placed on the category 3 list, with some safety concern regarding

methyl eugenol Methyl eugenol (allylveratrol) is a natural chemical compound classified as a phenylpropene, a type of phenylpropanoid. It is the methyl ether of eugenol and is important to insect behavior and pollination. It is found in various essential oils. ...

. In the UK, EU legislation governing insect repellents came into force in September 2006, which banned citronella as an active ingredient in any insect repellent products."HSE Biocides Unit responds to The Daily Telegraph article"
13 October 2006 This applied to insect repellent for both humans and other animals. It can still be sold as a perfume, but must not be sold as an insect repellent.

References

{{Reflist, 2 Biopesticides Essential oils Flavors