Citronella Essential Oil

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Citronella Essential Oil – General Description

Citronella essential oil is a volatile oil extracted from the leaves and stem of various perennial grass species of Cymbopogon, in particular C. nardus, through steam distillation method. It appears colorless or clear to yellowish with a distinct citrusy, sweet, fresh odor with subtle wood tones and a medium-strength initial aroma. ^[1] In addition, it also has a thin consistency and a top perfumery note ^[2] and can be categorized into two distinct chemotypes, namely Ceylon (derived from C. nardus Rendle) and Java (obtained from C. winterianus Jowitt). ^[1] To date, numerous scientific studies have claimed that citronella essential oil is inarguably one of the most industrially important essential oils. ^[3]

Citronella Essential Oil – Uses and Reported Benefits

Citronella essential oil has been mainly used in soap, perfumery, cosmetic, and flavoring industries and in the production of pharmaceutical products for health purposes. It is purported to have antiseptic, anti-inflammatory, antibacterial, antifungal, antiparasitic, stimulant, and tonic properties and constantly finds application in massages and skin and hair conditioning, although citronella essential oil is more popularly known for its insect repellent effect. Moreover, this essential oil can help remedy acne, fatigue, minor infection, muscle pain, flu, and colds. ^[4]

Citronella Essential Oil – Contraindications and Safety

A 2014 study from the University of Calcutta, India, explored the cytotoxic and genotoxic potential of four essential oils, namely, palmarosa, citronella, lemongrass, and vetiver essential oils, in human lymphocytes, a type of white blood cells vital to our immune system. This recent investigation confirmed that citronella essential oil is safe for consumption at low concentrations. ^[5] Citronella essential oil however may cause skin sensitization among allergic individuals, ^[4] and like any other essential oil, its use during pregnancy and lactation period is best avoided, especially if without the proper supervision of a qualified aromatherapy practitioner.

Citronella Essential Oil – Scientific Studies And Research

Citronella as antimicrobial, antivirus and antifungal:
A relatively good number of studies have reported the antimicrobial and antiparasitic effects of citronella essential oil against various species of bacteria, yeasts, filamentous fungi, and viruses. Pattnaik, Subramanyam, and Kole (1996) examined the antibacterial activity of ten essential oils, including citronella essential oil, against twenty-two Gram-positive cocci and rods and Gram-negative rods and twelve fungi using disc diffusion method. In this study, citronella essential oil was inhibitory to twelve bacterial strains and all twelve yeast-like and filamentous fungi tested. ^[6] In addition, de Billerbeck et al. (2001) claimed that citronella essential oil hampers the growth of Aspergillus niger mycelium at 800 mg/L, probably by interfering with the enzymes related to fungal wall synthesis and disrupting the fungi’s plasma membranes. This led these researchers to recommend the use of citronella essential oil as an efficacious, environmentally friendly inhibitor of biodegrading and storage-contaminating fungi. ^[7] Interestingly, such finding has been similarly reported by Li et al. (2013), who evaluated the antifungal action of citronella essential oil against A. niger ATCC 16404 using poisoned food technique, broth dilution method, and disc volatility method. The experimental results of Li et al. (2013) indicated the strong antifungal activity of citronella essential oil, which effectively inhibited the growth of conidia and caused an irreversible damage to the fungi’ hyphae. ^[8]

Citronella as anti-inflammatory: Employing broth microdilution technique, a group of researchers from Khon Kaen University, Thailand, sufficiently evidenced the potential anti-inflammatory role of citronella essential oil in relieving acne blemishes, which could possibly result in scar formation. In this study, the in vitro susceptibility of seven essential oils used heavily for skincare, including citronella essential oil, against Propionibacterium acnes was examined. Among the findings observed in this investigation include citronella essential oil having the lowest minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) at 0.005–0.3 and 0.6–1.2 μl/ml, respectively; an antioxidant activity IC50 value lower than that of ascorbic acid; and an anti-inflammatory activity IC50 value less than that of nordihydroquaretic acid. ^[9]

Sinha, Biswas, and Mukherjee (2011) demonstrated the significant dose-dependent antioxidant activity and the superior antigenotoxic effect of citronella essential oil on human lymphocytes against methyl methanesulfonate (MMS) and hydrogen peroxide, further scientifically supporting the usage of citronella essential oil in herbal preparations and as a natural source of safe antioxidants. ^[10]

Citronella as mosquito repellant: Much of citronella essential oil’s fame revolves around its research-verified utility as a safe, natural insect repellent. In 2005, a group of researchers from Mahidol University, Thailand, examined the mosquito repellent properties of 38 essential oils, including patchouli, clove, and citronella essential oils, which were applied on the forearms of human subjects at a concentration of 0.1 ml of oil per 30 square cm of exposed skin. The study showed that undiluted citronella essential oil can provide about 2 hours of absolute repellency and protection against the mosquitoes Aedes aegypti, Culex quinquefasciatus, and Anopheles dirus. ^[11]

Citronella as wasp repellant: Citronella essential oil has also been found to efficiently repel several species of pestiferous social wasps, mainly yellowjackets (Vespula pensylvanica (Saussure)) and paper wasps (Polistes dominulus (Christ)), ^[12] as well as human body lice ^[13] and head lice. ^[14]

Citronella against lice: In an earlier study conducted by a team of Israeli researchers from Hebrew University, citronella essential oil was deemed to be the most effective repellent against the human body louse, Pediculus humanus humanus, among the five essential oils tested in their study. Citronella’s repellency lasted for at least 29 days in this study and it remained effective at a dilution of 1:4. ^[13] Additionally, in 2004, a randomized, placebo-controlled, double-blind clinical study was conducted among children in four elementary schools to investigate the effectiveness of a slow-release citronella formulation as a repellent against head lice. Results from this study revealed the effectiveness of the citronella formulation as an anti-louse repellent, which reduced the incidence of louse reinfestations among children treated. ^[14]

Citronella Essential Oil – Molecular Components and Chemistry

Citronella essential oil prides in being a rich source of citronellal, citronellol, and geraniol, the Java variety of this essential oil having a higher geraniol and citronellol content than its Ceylon counterpart. ^[1] Wei and Wee (2013) chemically analyzed the composition of citronella essential oil through gas chromatography–mass spectroscopy in their study and had observed various chemical compounds, with citronellal representing the major compound and caryophyllene, citronellol, limonene, and eugenol as some of the essential oil’s minor constituents. ^[15] A recent 2014 study published in Industrial Crops and Products noted a significant increase in limonene (2.2–3.1%), citronellol (5.4–6.9%), and geraniol (19.2–26.7%) contents of citronella essential oil upon an increase in the age of plant. ^[3]