What is it?
An essential oil distilled from the leaves of citronella grass, Cymbopogon nardus, the source of the “Ceylon type” oil. Its main constituents include geraniol, methyl isoeugenol, limonene, citronellal and citronellol. It is best known as a plant-based insect repellent in sprays, rub-on products and candles, and it is also used as a fragrance in cosmetics.
Key information
- Citronella oil was first registered in the United States as an insect repellent in 1948, and the EPA considers it of low acute toxicity.
- The EPA classes the Ceylon-type oil made from Cymbopogon nardus as a weak skin sensitizer, while the Java type is not.
- Every batch of Cymbopogon nardus oil reviewed by EFSA in 2024 contained methyleugenol, at 0.41 to 1.00 percent.
- IARC classifies methyleugenol as probably carcinogenic to humans (Group 2A), based on animal and mechanistic evidence.
More information
Two kinds of citronella oil are sold: the Ceylon type from Cymbopogon nardus, profiled here, and the Java type from Cymbopogon winterianus. In four batches of C. nardus oil analyzed for the European Food Safety Authority (EFSA) in 2024, geraniol averaged about 17 percent and methyl isoeugenol about 12 percent of the oil, with smaller amounts of limonene, citronellal and citronellol.
In its 1997 review, the EPA found citronella oil to be of low acute toxicity in animal tests but classed the Ceylon type as a weak skin sensitizer. The EPA requires registered skin-applied repellents made from Ceylon-type oil to warn that prolonged or frequently repeated skin contact may cause allergic reactions in some people, and that use on children under 6 months should be only on a doctor’s advice. EFSA’s animal-feed panel likewise concluded that the oil itself should be considered irritating to skin and eyes and a skin sensitizer.
The bigger question is methyleugenol. EFSA found it in every batch it reviewed and describes it as genotoxic and carcinogenic in rodents. The World Health Organization’s cancer agency, IARC, classifies methyleugenol as probably carcinogenic to humans (Group 2A), based on sufficient evidence in experimental animals and strong mechanistic evidence; evidence in humans was inadequate. EU cosmetics law caps methyleugenol in finished products at 0.0002 percent in most leave-on products, 0.001 percent in rinse-off products and 0.01 percent in fine fragrance, which limits how much Ceylon citronella oil a product sold there can contain.
On labels, look for Cymbopogon Nardus Oil (Ceylon type) or Cymbopogon Winterianus Oil (Java type). Keep undiluted oil away from the eyes.
Sources: EPA: R.E.D. Facts, Oil of Citronella (1997); EFSA Journal (2024): Safety and efficacy of citronella oil from Cymbopogon nardus as a feed additive; IARC Monographs: Volume 134, Aspartame, methyleugenol, and isoeugenol; EUR-Lex: Regulation (EC) No 1223/2009 on cosmetic products, Annex III
